diff --git a/head/schema-cplusplus/test/inputs/schema/pattern-properties.schema/default/quicktype.hpp b/head/schema-cplusplus/test/inputs/schema/pattern-properties.schema/default/quicktype.hpp
new file mode 100644
index 0000000..84fd85a
--- /dev/null
+++ b/head/schema-cplusplus/test/inputs/schema/pattern-properties.schema/default/quicktype.hpp
@@ -0,0 +1,35 @@
+//  To parse this JSON data, first install
+//
+//      json.hpp  https://github.com/nlohmann/json
+//
+//  Then include this file, and then do
+//
+//     TopLevel data = nlohmann::json::parse(jsonString);
+
+#pragma once
+
+#include "json.hpp"
+
+#include <optional>
+#include <stdexcept>
+#include <regex>
+
+namespace quicktype {
+    using nlohmann::json;
+
+    #ifndef NLOHMANN_UNTYPED_quicktype_HELPER
+    #define NLOHMANN_UNTYPED_quicktype_HELPER
+    inline json get_untyped(const json & j, const char * property) {
+        if (j.find(property) != j.end()) {
+            return j.at(property).get<json>();
+        }
+        return json();
+    }
+
+    inline json get_untyped(const json & j, std::string property) {
+        return get_untyped(j, property.data());
+    }
+    #endif
+
+    using TopLevel = std::map<std::string, bool>;
+}
diff --git a/head/schema-csharp/test/inputs/schema/pattern-properties.schema/default/QuickType.cs b/head/schema-csharp/test/inputs/schema/pattern-properties.schema/default/QuickType.cs
new file mode 100644
index 0000000..1f76322
--- /dev/null
+++ b/head/schema-csharp/test/inputs/schema/pattern-properties.schema/default/QuickType.cs
@@ -0,0 +1,55 @@
+// <auto-generated />
+//
+// To parse this JSON data, add NuGet 'Newtonsoft.Json' then do:
+//
+//    using QuickType;
+//
+//    var topLevel = TopLevel.FromJson(jsonString);
+#nullable enable
+#pragma warning disable CS8618
+#pragma warning disable CS8601
+#pragma warning disable CS8602
+#pragma warning disable CS8603
+#pragma warning disable CS8604
+#pragma warning disable CS8625
+#pragma warning disable CS8765
+
+namespace QuickType
+{
+    using System;
+    using System.Collections.Generic;
+
+    using System.Globalization;
+    using Newtonsoft.Json;
+    using Newtonsoft.Json.Converters;
+
+    public class TopLevel
+    {
+        public static Dictionary<string, bool> FromJson(string json) => JsonConvert.DeserializeObject<Dictionary<string, bool>>(json, QuickType.Converter.Settings);
+    }
+
+    public static partial class Serialize
+    {
+        public static string ToJson(this Dictionary<string, bool> self) => JsonConvert.SerializeObject(self, QuickType.Converter.Settings);
+    }
+
+    internal static partial class Converter
+    {
+        public static readonly JsonSerializerSettings Settings = new JsonSerializerSettings
+        {
+            MetadataPropertyHandling = MetadataPropertyHandling.Ignore,
+            DateParseHandling = DateParseHandling.None,
+            Converters =
+            {
+                new IsoDateTimeConverter { DateTimeStyles = DateTimeStyles.AssumeUniversal }
+            },
+        };
+    }
+}
+#pragma warning restore CS8618
+#pragma warning restore CS8601
+#pragma warning restore CS8602
+#pragma warning restore CS8603
+#pragma warning restore CS8604
+#pragma warning restore CS8625
+#pragma warning restore CS8765
diff --git a/head/schema-csharp-SystemTextJson/test/inputs/schema/pattern-properties.schema/default/QuickType.cs b/head/schema-csharp-SystemTextJson/test/inputs/schema/pattern-properties.schema/default/QuickType.cs
new file mode 100644
index 0000000..5d149ce
--- /dev/null
+++ b/head/schema-csharp-SystemTextJson/test/inputs/schema/pattern-properties.schema/default/QuickType.cs
@@ -0,0 +1,159 @@
+// <auto-generated />
+//
+// To parse this JSON data, add NuGet 'System.Text.Json' then do:
+//
+//    using QuickType;
+//
+//    var topLevel = TopLevel.FromJson(jsonString);
+#nullable enable
+#pragma warning disable CS8618
+#pragma warning disable CS8601
+#pragma warning disable CS8602
+#pragma warning disable CS8603
+
+namespace QuickType
+{
+    using System;
+    using System.Collections.Generic;
+
+    using System.Text.Json;
+    using System.Text.Json.Serialization;
+    using System.Globalization;
+
+    public class TopLevel
+    {
+        public static Dictionary<string, bool> FromJson(string json) => JsonSerializer.Deserialize<Dictionary<string, bool>>(json, QuickType.Converter.Settings);
+    }
+
+    public static partial class Serialize
+    {
+        public static string ToJson(this Dictionary<string, bool> self) => JsonSerializer.Serialize(self, QuickType.Converter.Settings);
+    }
+
+    internal static partial class Converter
+    {
+        public static readonly JsonSerializerOptions Settings = new(JsonSerializerDefaults.General)
+        {
+            Converters =
+            {
+                new DateOnlyConverter(),
+                new TimeOnlyConverter(),
+                IsoDateTimeOffsetConverter.Singleton
+            },
+        };
+    }
+    
+    public class DateOnlyConverter : JsonConverter<DateOnly>
+    {
+        private readonly string serializationFormat;
+        public DateOnlyConverter() : this(null) { }
+
+        public DateOnlyConverter(string? serializationFormat)
+        {
+                this.serializationFormat = serializationFormat ?? "yyyy-MM-dd";
+        }
+
+        public override DateOnly Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+                var value = reader.GetString();
+                return DateOnly.Parse(value!);
+        }
+
+        public override void Write(Utf8JsonWriter writer, DateOnly value, JsonSerializerOptions options)
+                => writer.WriteStringValue(value.ToString(serializationFormat));
+    }
+
+    public class TimeOnlyConverter : JsonConverter<TimeOnly>
+    {
+        private readonly string serializationFormat;
+
+        public TimeOnlyConverter() : this(null) { }
+
+        public TimeOnlyConverter(string? serializationFormat)
+        {
+                this.serializationFormat = serializationFormat ?? "HH:mm:ss.fff";
+        }
+
+        public override TimeOnly Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+                var value = reader.GetString();
+                return TimeOnly.Parse(value!);
+        }
+
+        public override void Write(Utf8JsonWriter writer, TimeOnly value, JsonSerializerOptions options)
+                => writer.WriteStringValue(value.ToString(serializationFormat));
+    }
+
+    internal class IsoDateTimeOffsetConverter : JsonConverter<DateTimeOffset>
+    {
+        public override bool CanConvert(Type t) => t == typeof(DateTimeOffset);
+
+        private const string DefaultDateTimeFormat = "yyyy'-'MM'-'dd'T'HH':'mm':'ss.FFFFFFFK";
+
+        private DateTimeStyles _dateTimeStyles = DateTimeStyles.RoundtripKind;
+        private string? _dateTimeFormat;
+        private CultureInfo? _culture;
+
+        public DateTimeStyles DateTimeStyles
+        {
+                get => _dateTimeStyles;
+                set => _dateTimeStyles = value;
+        }
+
+        public string? DateTimeFormat
+        {
+                get => _dateTimeFormat ?? string.Empty;
+                set => _dateTimeFormat = (string.IsNullOrEmpty(value)) ? null : value;
+        }
+
+        public CultureInfo Culture
+        {
+                get => _culture ?? CultureInfo.CurrentCulture;
+                set => _culture = value;
+        }
+
+        public override void Write(Utf8JsonWriter writer, DateTimeOffset value, JsonSerializerOptions options)
+        {
+                string text;
+
+
+                if ((_dateTimeStyles & DateTimeStyles.AdjustToUniversal) == DateTimeStyles.AdjustToUniversal
+                        || (_dateTimeStyles & DateTimeStyles.AssumeUniversal) == DateTimeStyles.AssumeUniversal)
+                {
+                        value = value.ToUniversalTime();
+                }
+
+                text = value.ToString(_dateTimeFormat ?? DefaultDateTimeFormat, Culture);
+
+                writer.WriteStringValue(text);
+        }
+
+        public override DateTimeOffset Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+                string? dateText = reader.GetString();
+
+                if (string.IsNullOrEmpty(dateText) == false)
+                {
+                        if (!string.IsNullOrEmpty(_dateTimeFormat))
+                        {
+                                return DateTimeOffset.ParseExact(dateText, _dateTimeFormat, Culture, _dateTimeStyles);
+                        }
+                        else
+                        {
+                                return DateTimeOffset.Parse(dateText, Culture, _dateTimeStyles);
+                        }
+                }
+                else
+                {
+                        return default(DateTimeOffset);
+                }
+        }
+
+
+        public static readonly IsoDateTimeOffsetConverter Singleton = new IsoDateTimeOffsetConverter();
+    }
+}
+#pragma warning restore CS8618
+#pragma warning restore CS8601
+#pragma warning restore CS8602
+#pragma warning restore CS8603
diff --git a/head/schema-csharp-records/test/inputs/schema/pattern-properties.schema/default/QuickType.cs b/head/schema-csharp-records/test/inputs/schema/pattern-properties.schema/default/QuickType.cs
new file mode 100644
index 0000000..1f76322
--- /dev/null
+++ b/head/schema-csharp-records/test/inputs/schema/pattern-properties.schema/default/QuickType.cs
@@ -0,0 +1,55 @@
+// <auto-generated />
+//
+// To parse this JSON data, add NuGet 'Newtonsoft.Json' then do:
+//
+//    using QuickType;
+//
+//    var topLevel = TopLevel.FromJson(jsonString);
+#nullable enable
+#pragma warning disable CS8618
+#pragma warning disable CS8601
+#pragma warning disable CS8602
+#pragma warning disable CS8603
+#pragma warning disable CS8604
+#pragma warning disable CS8625
+#pragma warning disable CS8765
+
+namespace QuickType
+{
+    using System;
+    using System.Collections.Generic;
+
+    using System.Globalization;
+    using Newtonsoft.Json;
+    using Newtonsoft.Json.Converters;
+
+    public class TopLevel
+    {
+        public static Dictionary<string, bool> FromJson(string json) => JsonConvert.DeserializeObject<Dictionary<string, bool>>(json, QuickType.Converter.Settings);
+    }
+
+    public static partial class Serialize
+    {
+        public static string ToJson(this Dictionary<string, bool> self) => JsonConvert.SerializeObject(self, QuickType.Converter.Settings);
+    }
+
+    internal static partial class Converter
+    {
+        public static readonly JsonSerializerSettings Settings = new JsonSerializerSettings
+        {
+            MetadataPropertyHandling = MetadataPropertyHandling.Ignore,
+            DateParseHandling = DateParseHandling.None,
+            Converters =
+            {
+                new IsoDateTimeConverter { DateTimeStyles = DateTimeStyles.AssumeUniversal }
+            },
+        };
+    }
+}
+#pragma warning restore CS8618
+#pragma warning restore CS8601
+#pragma warning restore CS8602
+#pragma warning restore CS8603
+#pragma warning restore CS8604
+#pragma warning restore CS8625
+#pragma warning restore CS8765
diff --git a/head/schema-dart/test/inputs/schema/pattern-properties.schema/default/TopLevel.dart b/head/schema-dart/test/inputs/schema/pattern-properties.schema/default/TopLevel.dart
new file mode 100644
index 0000000..1194450
--- /dev/null
+++ b/head/schema-dart/test/inputs/schema/pattern-properties.schema/default/TopLevel.dart
@@ -0,0 +1,9 @@
+// To parse this JSON data, do
+//
+//     final topLevel = topLevelFromJson(jsonString);
+
+import 'dart:convert';
+
+Map<String, bool> topLevelFromJson(String str) => Map.from(json.decode(str)).map((k, v) => MapEntry<String, bool>(k, v));
+
+String topLevelToJson(Map<String, bool> data) => json.encode(Map.from(data).map((k, v) => MapEntry<String, dynamic>(k, v)));
diff --git a/head/schema-elm/test/inputs/schema/pattern-properties.schema/default/QuickType.elm b/head/schema-elm/test/inputs/schema/pattern-properties.schema/default/QuickType.elm
new file mode 100644
index 0000000..812cb6a
--- /dev/null
+++ b/head/schema-elm/test/inputs/schema/pattern-properties.schema/default/QuickType.elm
@@ -0,0 +1,41 @@
+-- To decode the JSON data, add this file to your project, run
+--
+--     elm install NoRedInk/elm-json-decode-pipeline
+--
+-- add these imports
+--
+--     import Json.Decode exposing (decodeString)
+--     import QuickType exposing (quickType)
+--
+-- and you're off to the races with
+--
+--     decodeString quickType myJsonString
+
+module QuickType exposing
+    ( QuickType
+    , quickTypeToString
+    , quickType
+    )
+
+import Json.Decode as Jdec
+import Json.Decode.Pipeline as Jpipe
+import Json.Encode as Jenc
+import Dict exposing (Dict)
+
+type alias QuickType = Dict String Bool
+
+-- decoders and encoders
+
+quickType : Jdec.Decoder QuickType
+quickType = Jdec.dict Jdec.bool
+
+quickTypeToString : QuickType -> String
+quickTypeToString r = Jenc.encode 0 (Jenc.dict identity Jenc.bool r)
+
+--- encoder helpers
+
+makeNullableEncoder : (a -> Jenc.Value) -> Maybe a -> Jenc.Value
+makeNullableEncoder f m =
+    case m of
+    Just x -> f x
+    Nothing -> Jenc.null
diff --git a/head/schema-flow/test/inputs/schema/pattern-properties.schema/default/TopLevel.js b/head/schema-flow/test/inputs/schema/pattern-properties.schema/default/TopLevel.js
new file mode 100644
index 0000000..30635fd
--- /dev/null
+++ b/head/schema-flow/test/inputs/schema/pattern-properties.schema/default/TopLevel.js
@@ -0,0 +1,181 @@
+// @flow
+
+// To parse this data:
+//
+//   const Convert = require("./TopLevel");
+//
+//   const topLevel = Convert.toTopLevel(json);
+//
+// These functions will throw an error if the JSON doesn't
+// match the expected interface, even if the JSON is valid.
+
+// Converts JSON strings to/from your types
+// and asserts the results of JSON.parse at runtime
+function toTopLevel(json: string): { [key: string]: boolean } {
+    return cast(JSON.parse(json), m(true));
+}
+
+function topLevelToJson(value: { [key: string]: boolean }): string {
+    return JSON.stringify(uncast(value, m(true)), null, 2);
+}
+
+function invalidValue(typ: any, val: any, key: any, parent: any = '') {
+    const prettyTyp = prettyTypeName(typ);
+    const parentText = parent ? ` on ${parent}` : '';
+    const keyText = key ? ` for key "${key}"` : '';
+    throw Error(`Invalid value${keyText}${parentText}. Expected ${prettyTyp} but got ${JSON.stringify(val)}`);
+}
+
+function prettyTypeName(typ: any): string {
+    if (Array.isArray(typ)) {
+        if (typ.length === 2 && typ[0] === undefined) {
+            return `an optional ${prettyTypeName(typ[1])}`;
+        } else {
+            return `one of [${typ.map(a => { return prettyTypeName(a); }).join(", ")}]`;
+        }
+    } else if (typeof typ === "object" && typ.literal !== undefined) {
+        return typ.literal;
+    } else {
+        return typeof typ;
+    }
+}
+
+function jsonToJSProps(typ: any): any {
+    if (typ.jsonToJS === undefined) {
+        const map: any = {};
+        typ.props.forEach((p: any) => map[p.json] = { key: p.js, typ: p.typ });
+        typ.jsonToJS = map;
+    }
+    return typ.jsonToJS;
+}
+
+function jsToJSONProps(typ: any): any {
+    if (typ.jsToJSON === undefined) {
+        const map: any = {};
+        typ.props.forEach((p: any) => map[p.js] = { key: p.json, typ: p.typ });
+        typ.jsToJSON = map;
+    }
+    return typ.jsToJSON;
+}
+
+function transform(val: any, typ: any, getProps: any, key: any = '', parent: any = ''): any {
+    function transformPrimitive(typ: string, val: any): any {
+        if (typeof typ === typeof val) return val;
+        return invalidValue(typ, val, key, parent);
+    }
+
+    function transformUnion(typs: any[], val: any): any {
+        // val must validate against one typ in typs
+        const l = typs.length;
+        for (let i = 0; i < l; i++) {
+            const typ = typs[i];
+            try {
+                return transform(val, typ, getProps);
+            } catch (_) {}
+        }
+        return invalidValue(typs, val, key, parent);
+    }
+
+    function transformEnum(cases: string[], val: any): any {
+        if (cases.indexOf(val) !== -1) return val;
+        return invalidValue(cases.map(a => { return l(a); }), val, key, parent);
+    }
+
+    function transformArray(typ: any, val: any): any {
+        // val must be an array with no invalid elements
+        if (!Array.isArray(val)) return invalidValue(l("array"), val, key, parent);
+        return val.map(el => transform(el, typ, getProps));
+    }
+
+    function transformDate(val: any): any {
+        if (val === null) {
+            return null;
+        }
+        const d = new Date(val);
+        if (isNaN(d.valueOf())) {
+            return invalidValue(l("Date"), val, key, parent);
+        }
+        return d;
+    }
+
+    function transformObject(props: { [k: string]: any }, additional: any, val: any): any {
+        if (val === null || typeof val !== "object" || Array.isArray(val)) {
+            return invalidValue(l(ref || "object"), val, key, parent);
+        }
+        const result: any = {};
+        Object.getOwnPropertyNames(props).forEach(key => {
+            const prop = props[key];
+            const v = Object.prototype.hasOwnProperty.call(val, key) ? val[key] : undefined;
+            result[prop.key] = transform(v, prop.typ, getProps, key, ref);
+        });
+        Object.getOwnPropertyNames(val).forEach(key => {
+            if (!Object.prototype.hasOwnProperty.call(props, key)) {
+                result[key] = transform(val[key], additional, getProps, key, ref);
+            }
+        });
+        return result;
+    }
+
+    if (typ === "any") return val;
+    if (typ === null) {
+        if (val === null) return val;
+        return invalidValue(typ, val, key, parent);
+    }
+    if (typ === false) return invalidValue(typ, val, key, parent);
+    let ref: any = undefined;
+    while (typeof typ === "object" && typ.ref !== undefined) {
+        ref = typ.ref;
+        typ = typeMap[typ.ref];
+    }
+    if (Array.isArray(typ)) return transformEnum(typ, val);
+    if (typeof typ === "object") {
+        return typ.hasOwnProperty("unionMembers") ? transformUnion(typ.unionMembers, val)
+            : typ.hasOwnProperty("arrayItems")    ? transformArray(typ.arrayItems, val)
+            : typ.hasOwnProperty("props")         ? transformObject(getProps(typ), typ.additional, val)
+            : invalidValue(typ, val, key, parent);
+    }
+    // Numbers can be parsed by Date but shouldn't be.
+    if (typ === Date && typeof val !== "number") return transformDate(val);
+    return transformPrimitive(typ, val);
+}
+
+function cast<T>(val: any, typ: any): T {
+    return transform(val, typ, jsonToJSProps);
+}
+
+function uncast<T>(val: T, typ: any): any {
+    return transform(val, typ, jsToJSONProps);
+}
+
+function l(typ: any) {
+    return { literal: typ };
+}
+
+function a(typ: any) {
+    return { arrayItems: typ };
+}
+
+function u(...typs: any[]) {
+    return { unionMembers: typs };
+}
+
+function o(props: any[], additional: any) {
+    return { props, additional };
+}
+
+function m(additional: any) {
+    const props: any[] = [];
+    return { props, additional };
+}
+
+function r(name: string) {
+    return { ref: name };
+}
+
+const typeMap: any = {
+};
+
+module.exports = {
+    "topLevelToJson": topLevelToJson,
+    "toTopLevel": toTopLevel,
+};
diff --git a/head/schema-golang/test/inputs/schema/pattern-properties.schema/default/quicktype.go b/head/schema-golang/test/inputs/schema/pattern-properties.schema/default/quicktype.go
new file mode 100644
index 0000000..cd8144a
--- /dev/null
+++ b/head/schema-golang/test/inputs/schema/pattern-properties.schema/default/quicktype.go
@@ -0,0 +1,21 @@
+// Code generated from JSON Schema using quicktype. DO NOT EDIT.
+// To parse and unparse this JSON data, add this code to your project and do:
+//
+//    topLevel, err := UnmarshalTopLevel(bytes)
+//    bytes, err = topLevel.Marshal()
+
+package main
+
+import "encoding/json"
+
+type TopLevel map[string]bool
+
+func UnmarshalTopLevel(data []byte) (TopLevel, error) {
+	var r TopLevel
+	err := json.Unmarshal(data, &r)
+	return r, err
+}
+
+func (r *TopLevel) Marshal() ([]byte, error) {
+	return json.Marshal(r)
+}
diff --git a/head/schema-javascript/test/inputs/schema/pattern-properties.schema/default/TopLevel.js b/head/schema-javascript/test/inputs/schema/pattern-properties.schema/default/TopLevel.js
new file mode 100644
index 0000000..9a9ca85
--- /dev/null
+++ b/head/schema-javascript/test/inputs/schema/pattern-properties.schema/default/TopLevel.js
@@ -0,0 +1,179 @@
+// To parse this data:
+//
+//   const Convert = require("./TopLevel");
+//
+//   const topLevel = Convert.toTopLevel(json);
+//
+// These functions will throw an error if the JSON doesn't
+// match the expected interface, even if the JSON is valid.
+
+// Converts JSON strings to/from your types
+// and asserts the results of JSON.parse at runtime
+function toTopLevel(json) {
+    return cast(JSON.parse(json), m(true));
+}
+
+function topLevelToJson(value) {
+    return JSON.stringify(uncast(value, m(true)), null, 2);
+}
+
+function invalidValue(typ, val, key, parent = '') {
+    const prettyTyp = prettyTypeName(typ);
+    const parentText = parent ? ` on ${parent}` : '';
+    const keyText = key ? ` for key "${key}"` : '';
+    throw Error(`Invalid value${keyText}${parentText}. Expected ${prettyTyp} but got ${JSON.stringify(val)}`);
+}
+
+function prettyTypeName(typ) {
+    if (Array.isArray(typ)) {
+        if (typ.length === 2 && typ[0] === undefined) {
+            return `an optional ${prettyTypeName(typ[1])}`;
+        } else {
+            return `one of [${typ.map(a => { return prettyTypeName(a); }).join(", ")}]`;
+        }
+    } else if (typeof typ === "object" && typ.literal !== undefined) {
+        return typ.literal;
+    } else {
+        return typeof typ;
+    }
+}
+
+function jsonToJSProps(typ) {
+    if (typ.jsonToJS === undefined) {
+        const map = {};
+        typ.props.forEach((p) => map[p.json] = { key: p.js, typ: p.typ });
+        typ.jsonToJS = map;
+    }
+    return typ.jsonToJS;
+}
+
+function jsToJSONProps(typ) {
+    if (typ.jsToJSON === undefined) {
+        const map = {};
+        typ.props.forEach((p) => map[p.js] = { key: p.json, typ: p.typ });
+        typ.jsToJSON = map;
+    }
+    return typ.jsToJSON;
+}
+
+function transform(val, typ, getProps, key = '', parent = '') {
+    function transformPrimitive(typ, val) {
+        if (typeof typ === typeof val) return val;
+        return invalidValue(typ, val, key, parent);
+    }
+
+    function transformUnion(typs, val) {
+        // val must validate against one typ in typs
+        const l = typs.length;
+        for (let i = 0; i < l; i++) {
+            const typ = typs[i];
+            try {
+                return transform(val, typ, getProps);
+            } catch (_) {}
+        }
+        return invalidValue(typs, val, key, parent);
+    }
+
+    function transformEnum(cases, val) {
+        if (cases.indexOf(val) !== -1) return val;
+        return invalidValue(cases.map(a => { return l(a); }), val, key, parent);
+    }
+
+    function transformArray(typ, val) {
+        // val must be an array with no invalid elements
+        if (!Array.isArray(val)) return invalidValue(l("array"), val, key, parent);
+        return val.map(el => transform(el, typ, getProps));
+    }
+
+    function transformDate(val) {
+        if (val === null) {
+            return null;
+        }
+        const d = new Date(val);
+        if (isNaN(d.valueOf())) {
+            return invalidValue(l("Date"), val, key, parent);
+        }
+        return d;
+    }
+
+    function transformObject(props, additional, val) {
+        if (val === null || typeof val !== "object" || Array.isArray(val)) {
+            return invalidValue(l(ref || "object"), val, key, parent);
+        }
+        const result = {};
+        Object.getOwnPropertyNames(props).forEach(key => {
+            const prop = props[key];
+            const v = Object.prototype.hasOwnProperty.call(val, key) ? val[key] : undefined;
+            result[prop.key] = transform(v, prop.typ, getProps, key, ref);
+        });
+        Object.getOwnPropertyNames(val).forEach(key => {
+            if (!Object.prototype.hasOwnProperty.call(props, key)) {
+                result[key] = transform(val[key], additional, getProps, key, ref);
+            }
+        });
+        return result;
+    }
+
+    if (typ === "any") return val;
+    if (typ === null) {
+        if (val === null) return val;
+        return invalidValue(typ, val, key, parent);
+    }
+    if (typ === false) return invalidValue(typ, val, key, parent);
+    let ref = undefined;
+    while (typeof typ === "object" && typ.ref !== undefined) {
+        ref = typ.ref;
+        typ = typeMap[typ.ref];
+    }
+    if (Array.isArray(typ)) return transformEnum(typ, val);
+    if (typeof typ === "object") {
+        return typ.hasOwnProperty("unionMembers") ? transformUnion(typ.unionMembers, val)
+            : typ.hasOwnProperty("arrayItems")    ? transformArray(typ.arrayItems, val)
+            : typ.hasOwnProperty("props")         ? transformObject(getProps(typ), typ.additional, val)
+            : invalidValue(typ, val, key, parent);
+    }
+    // Numbers can be parsed by Date but shouldn't be.
+    if (typ === Date && typeof val !== "number") return transformDate(val);
+    return transformPrimitive(typ, val);
+}
+
+function cast(val, typ) {
+    return transform(val, typ, jsonToJSProps);
+}
+
+function uncast(val, typ) {
+    return transform(val, typ, jsToJSONProps);
+}
+
+function l(typ) {
+    return { literal: typ };
+}
+
+function a(typ) {
+    return { arrayItems: typ };
+}
+
+function u(...typs) {
+    return { unionMembers: typs };
+}
+
+function o(props, additional) {
+    return { props, additional };
+}
+
+function m(additional) {
+    const props = [];
+    return { props, additional };
+}
+
+function r(name) {
+    return { ref: name };
+}
+
+const typeMap = {
+};
+
+module.exports = {
+    "topLevelToJson": topLevelToJson,
+    "toTopLevel": toTopLevel,
+};
diff --git a/head/schema-kotlinx/test/inputs/schema/pattern-properties.schema/default/TopLevel.kt b/head/schema-kotlinx/test/inputs/schema/pattern-properties.schema/default/TopLevel.kt
new file mode 100644
index 0000000..0db3087
--- /dev/null
+++ b/head/schema-kotlinx/test/inputs/schema/pattern-properties.schema/default/TopLevel.kt
@@ -0,0 +1,13 @@
+// To parse the JSON, install kotlin's serialization plugin and do:
+//
+// val json     = Json { allowStructuredMapKeys = true }
+// val topLevel = json.parse(TopLevel.serializer(), jsonString)
+
+package quicktype
+
+import kotlinx.serialization.*
+import kotlinx.serialization.json.*
+import kotlinx.serialization.descriptors.*
+import kotlinx.serialization.encoding.*
+
+typealias TopLevel = HashMap<String, Boolean>
diff --git a/head/schema-python/test/inputs/schema/pattern-properties.schema/default/quicktype.py b/head/schema-python/test/inputs/schema/pattern-properties.schema/default/quicktype.py
new file mode 100644
index 0000000..d558c9f
--- /dev/null
+++ b/head/schema-python/test/inputs/schema/pattern-properties.schema/default/quicktype.py
@@ -0,0 +1,22 @@
+from typing import Any, TypeVar, Callable
+
+
+T = TypeVar("T")
+
+
+def from_dict(f: Callable[[Any], T], x: Any) -> dict[str, T]:
+    assert isinstance(x, dict)
+    return { k: f(v) for (k, v) in x.items() }
+
+
+def from_bool(x: Any) -> bool:
+    assert isinstance(x, bool)
+    return x
+
+
+def top_level_from_dict(s: Any) -> dict[str, bool]:
+    return from_dict(from_bool, s)
+
+
+def top_level_to_dict(x: dict[str, bool]) -> Any:
+    return from_dict(from_bool, x)
diff --git a/head/schema-ruby/test/inputs/schema/pattern-properties.schema/default/TopLevel.rb b/head/schema-ruby/test/inputs/schema/pattern-properties.schema/default/TopLevel.rb
new file mode 100644
index 0000000..65f6097
--- /dev/null
+++ b/head/schema-ruby/test/inputs/schema/pattern-properties.schema/default/TopLevel.rb
@@ -0,0 +1,26 @@
+# This code may look unusually verbose for Ruby (and it is), but
+# it performs some subtle and complex validation of JSON data.
+#
+# To parse this JSON, add 'dry-struct' and 'dry-types' gems, then do:
+#
+#   top_level = TopLevel.from_json! "{…}"
+#   puts top_level["…"]
+#
+# If from_json! succeeds, the value returned matches the schema.
+
+require 'json'
+require 'dry-types'
+require 'dry-struct'
+
+module Types
+  include Dry.Types(default: :nominal)
+
+  Bool = Strict::Bool
+  Hash = Strict::Hash
+end
+
+class TopLevel
+  def self.from_json!(json)
+    Types::Hash[JSON.parse(json, quirks_mode: true)].map { |k, v| [k, Types::Bool[v]] }.to_h
+  end
+end
diff --git a/head/schema-rust/test/inputs/schema/pattern-properties.schema/default/module_under_test.rs b/head/schema-rust/test/inputs/schema/pattern-properties.schema/default/module_under_test.rs
new file mode 100644
index 0000000..237160a
--- /dev/null
+++ b/head/schema-rust/test/inputs/schema/pattern-properties.schema/default/module_under_test.rs
@@ -0,0 +1,17 @@
+// Example code that deserializes and serializes the model.
+// extern crate serde;
+// #[macro_use]
+// extern crate serde_derive;
+// extern crate serde_json;
+//
+// use generated_module::TopLevel;
+//
+// fn main() {
+//     let json = r#"{"answer": 42}"#;
+//     let model: TopLevel = serde_json::from_str(&json).unwrap();
+// }
+
+use serde::{Serialize, Deserialize};
+use std::collections::HashMap;
+
+pub type TopLevel = HashMap<String, bool>;
diff --git a/head/schema-scala3/test/inputs/schema/pattern-properties.schema/default/TopLevel.scala b/head/schema-scala3/test/inputs/schema/pattern-properties.schema/default/TopLevel.scala
new file mode 100644
index 0000000..bea693c
--- /dev/null
+++ b/head/schema-scala3/test/inputs/schema/pattern-properties.schema/default/TopLevel.scala
@@ -0,0 +1,12 @@
+package quicktype
+
+import io.circe.syntax._
+import io.circe._
+import cats.syntax.functor._
+
+// If a union has a null in, then we'll need this too... 
+type NullValue = None.type
+
+type TopLevel = Map[String, Boolean]
+
+given (using ev : Boolean): Encoder[Map[String, Boolean]] = Encoder.encodeMap[String, Boolean]
diff --git a/head/schema-scala3-upickle/test/inputs/schema/pattern-properties.schema/default/TopLevel.scala b/head/schema-scala3-upickle/test/inputs/schema/pattern-properties.schema/default/TopLevel.scala
new file mode 100644
index 0000000..20f420f
--- /dev/null
+++ b/head/schema-scala3-upickle/test/inputs/schema/pattern-properties.schema/default/TopLevel.scala
@@ -0,0 +1,68 @@
+package quicktype
+
+// Custom pickler so that missing keys and JSON nulls both read as None,
+// and None is left out when writing (upickle's default for Option is a
+// JSON array).
+object OptionPickler extends upickle.AttributeTagged:
+    import upickle.default.Writer
+    import upickle.default.Reader
+    override implicit def OptionWriter[T: Writer]: Writer[Option[T]] =
+        implicitly[Writer[T]].comap[Option[T]] {
+            case None => null.asInstanceOf[T]
+            case Some(x) => x
+        }
+
+    override implicit def OptionReader[T: Reader]: Reader[Option[T]] = {
+        new Reader.Delegate[Any, Option[T]](implicitly[Reader[T]].map(Some(_))){
+        override def visitNull(index: Int) = None
+        }
+    }
+end OptionPickler
+
+// If a union has a null in, then we'll need this too...
+type NullValue = None.type
+given OptionPickler.ReadWriter[NullValue] = OptionPickler.readwriter[ujson.Value].bimap[NullValue](
+    _ => ujson.Null,
+    json => if json.isNull then None else throw new upickle.core.Abort("not null")
+)
+
+object JsonExt:
+    val valueReader = OptionPickler.readwriter[ujson.Value]
+
+    // upickle's built-in primitive readers are lenient -- the numeric and
+    // boolean readers accept strings, and the string reader accepts
+    // numbers and booleans -- so untagged unions need strict readers to
+    // pick the right member.
+    val strictString: OptionPickler.Reader[String] = valueReader.map {
+        case ujson.Str(s) => s
+        case json => throw new upickle.core.Abort("expected string, got " + json)
+    }
+    val strictLong: OptionPickler.Reader[Long] = valueReader.map {
+        case ujson.Num(n) if n.isWhole => n.toLong
+        case json => throw new upickle.core.Abort("expected integer, got " + json)
+    }
+    val strictDouble: OptionPickler.Reader[Double] = valueReader.map {
+        case ujson.Num(n) => n
+        case json => throw new upickle.core.Abort("expected number, got " + json)
+    }
+    val strictBoolean: OptionPickler.Reader[Boolean] = valueReader.map {
+        case ujson.Bool(b) => b
+        case json => throw new upickle.core.Abort("expected boolean, got " + json)
+    }
+
+    def badMerge[T](r1: => OptionPickler.Reader[?], rest: OptionPickler.Reader[?]*): OptionPickler.Reader[T] = valueReader.map { json =>
+        var t: T | Null = null
+        val stack       = Vector.newBuilder[Throwable]
+        (r1 +: rest).foreach { reader =>
+            if t == null then
+            try
+                t = OptionPickler.read[T](json, trace = true)(using reader.asInstanceOf[OptionPickler.Reader[T]])
+            catch
+                case exc => stack += exc
+        }
+        if t != null then t.nn else throw new Exception(json.toString(), stack.result().headOption.getOrElse(null))
+    }
+end JsonExt
+
+
+type TopLevel = Map[String, Boolean]
diff --git a/head/schema-schema/test/inputs/schema/pattern-properties.schema/default/TopLevel.schema b/head/schema-schema/test/inputs/schema/pattern-properties.schema/default/TopLevel.schema
new file mode 100644
index 0000000..f429443
--- /dev/null
+++ b/head/schema-schema/test/inputs/schema/pattern-properties.schema/default/TopLevel.schema
@@ -0,0 +1,8 @@
+{
+    "$schema": "http://json-schema.org/draft-06/schema#",
+    "type": "object",
+    "additionalProperties": {
+        "type": "boolean"
+    },
+    "definitions": {}
+}
diff --git a/head/schema-typescript/test/inputs/schema/pattern-properties.schema/default/TopLevel.ts b/head/schema-typescript/test/inputs/schema/pattern-properties.schema/default/TopLevel.ts
new file mode 100644
index 0000000..ec99fba
--- /dev/null
+++ b/head/schema-typescript/test/inputs/schema/pattern-properties.schema/default/TopLevel.ts
@@ -0,0 +1,176 @@
+// To parse this data:
+//
+//   import { Convert } from "./TopLevel";
+//
+//   const topLevel = Convert.toTopLevel(json);
+//
+// These functions will throw an error if the JSON doesn't
+// match the expected interface, even if the JSON is valid.
+
+// Converts JSON strings to/from your types
+// and asserts the results of JSON.parse at runtime
+export class Convert {
+    public static toTopLevel(json: string): { [key: string]: boolean } {
+        return cast(JSON.parse(json), m(true));
+    }
+
+    public static topLevelToJson(value: { [key: string]: boolean }): string {
+        return JSON.stringify(uncast(value, m(true)), null, 2);
+    }
+}
+
+function invalidValue(typ: any, val: any, key: any, parent: any = ''): never {
+    const prettyTyp = prettyTypeName(typ);
+    const parentText = parent ? ` on ${parent}` : '';
+    const keyText = key ? ` for key "${key}"` : '';
+    throw Error(`Invalid value${keyText}${parentText}. Expected ${prettyTyp} but got ${JSON.stringify(val)}`);
+}
+
+function prettyTypeName(typ: any): string {
+    if (Array.isArray(typ)) {
+        if (typ.length === 2 && typ[0] === undefined) {
+            return `an optional ${prettyTypeName(typ[1])}`;
+        } else {
+            return `one of [${typ.map(a => { return prettyTypeName(a); }).join(", ")}]`;
+        }
+    } else if (typeof typ === "object" && typ.literal !== undefined) {
+        return typ.literal;
+    } else {
+        return typeof typ;
+    }
+}
+
+function jsonToJSProps(typ: any): any {
+    if (typ.jsonToJS === undefined) {
+        const map: any = {};
+        typ.props.forEach((p: any) => map[p.json] = { key: p.js, typ: p.typ });
+        typ.jsonToJS = map;
+    }
+    return typ.jsonToJS;
+}
+
+function jsToJSONProps(typ: any): any {
+    if (typ.jsToJSON === undefined) {
+        const map: any = {};
+        typ.props.forEach((p: any) => map[p.js] = { key: p.json, typ: p.typ });
+        typ.jsToJSON = map;
+    }
+    return typ.jsToJSON;
+}
+
+function transform(val: any, typ: any, getProps: any, key: any = '', parent: any = ''): any {
+    function transformPrimitive(typ: string, val: any): any {
+        if (typeof typ === typeof val) return val;
+        return invalidValue(typ, val, key, parent);
+    }
+
+    function transformUnion(typs: any[], val: any): any {
+        // val must validate against one typ in typs
+        const l = typs.length;
+        for (let i = 0; i < l; i++) {
+            const typ = typs[i];
+            try {
+                return transform(val, typ, getProps);
+            } catch (_) {}
+        }
+        return invalidValue(typs, val, key, parent);
+    }
+
+    function transformEnum(cases: string[], val: any): any {
+        if (cases.indexOf(val) !== -1) return val;
+        return invalidValue(cases.map(a => { return l(a); }), val, key, parent);
+    }
+
+    function transformArray(typ: any, val: any): any {
+        // val must be an array with no invalid elements
+        if (!Array.isArray(val)) return invalidValue(l("array"), val, key, parent);
+        return val.map(el => transform(el, typ, getProps));
+    }
+
+    function transformDate(val: any): any {
+        if (val === null) {
+            return null;
+        }
+        const d = new Date(val);
+        if (isNaN(d.valueOf())) {
+            return invalidValue(l("Date"), val, key, parent);
+        }
+        return d;
+    }
+
+    function transformObject(props: { [k: string]: any }, additional: any, val: any): any {
+        if (val === null || typeof val !== "object" || Array.isArray(val)) {
+            return invalidValue(l(ref || "object"), val, key, parent);
+        }
+        const result: any = {};
+        Object.getOwnPropertyNames(props).forEach(key => {
+            const prop = props[key];
+            const v = Object.prototype.hasOwnProperty.call(val, key) ? val[key] : undefined;
+            result[prop.key] = transform(v, prop.typ, getProps, key, ref);
+        });
+        Object.getOwnPropertyNames(val).forEach(key => {
+            if (!Object.prototype.hasOwnProperty.call(props, key)) {
+                result[key] = transform(val[key], additional, getProps, key, ref);
+            }
+        });
+        return result;
+    }
+
+    if (typ === "any") return val;
+    if (typ === null) {
+        if (val === null) return val;
+        return invalidValue(typ, val, key, parent);
+    }
+    if (typ === false) return invalidValue(typ, val, key, parent);
+    let ref: any = undefined;
+    while (typeof typ === "object" && typ.ref !== undefined) {
+        ref = typ.ref;
+        typ = typeMap[typ.ref];
+    }
+    if (Array.isArray(typ)) return transformEnum(typ, val);
+    if (typeof typ === "object") {
+        return typ.hasOwnProperty("unionMembers") ? transformUnion(typ.unionMembers, val)
+            : typ.hasOwnProperty("arrayItems")    ? transformArray(typ.arrayItems, val)
+            : typ.hasOwnProperty("props")         ? transformObject(getProps(typ), typ.additional, val)
+            : invalidValue(typ, val, key, parent);
+    }
+    // Numbers can be parsed by Date but shouldn't be.
+    if (typ === Date && typeof val !== "number") return transformDate(val);
+    return transformPrimitive(typ, val);
+}
+
+function cast<T>(val: any, typ: any): T {
+    return transform(val, typ, jsonToJSProps);
+}
+
+function uncast<T>(val: T, typ: any): any {
+    return transform(val, typ, jsToJSONProps);
+}
+
+function l(typ: any) {
+    return { literal: typ };
+}
+
+function a(typ: any) {
+    return { arrayItems: typ };
+}
+
+function u(...typs: any[]) {
+    return { unionMembers: typs };
+}
+
+function o(props: any[], additional: any) {
+    return { props, additional };
+}
+
+function m(additional: any) {
+    const props: any[] = [];
+    return { props, additional };
+}
+
+function r(name: string) {
+    return { ref: name };
+}
+
+const typeMap: any = {
+};