diff --git a/swagger_parser/CHANGELOG.md b/swagger_parser/CHANGELOG.md
index 8f45c2756..1c23a9819 100644
--- a/swagger_parser/CHANGELOG.md
+++ b/swagger_parser/CHANGELOG.md
@@ -1,3 +1,9 @@
+## 1.45.1
+
+* Fixes OpenAPI 3 schemas without a `required` array generating every property as `required`
+  when any property uses `allOf`
+  ([#460](https://github.com/Carapacik/swagger_parser/issues/460)).
+
 ## 1.45.0
 
 * Adds `freezed_json_serialization` (default `true`) to generate Freezed models
diff --git a/swagger_parser/lib/src/parser/parser/open_api_parser.dart b/swagger_parser/lib/src/parser/parser/open_api_parser.dart
index 32a1b7641..257a1f7c2 100644
--- a/swagger_parser/lib/src/parser/parser/open_api_parser.dart
+++ b/swagger_parser/lib/src/parser/parser/open_api_parser.dart
@@ -766,16 +766,8 @@ class OpenApiParser {
     final imports = <String>{};
 
     var requiredParameters = <String>[];
-    var hasAllOfKey = false;
     if (map case {_requiredConst: final List<dynamic> rawParameters}) {
       requiredParameters = rawParameters.map((e) => e.toString()).toList();
-    } else if (map case {_propertiesConst: final Map<String, dynamic> props}) {
-      for (final propertyName in props.keys) {
-        final propertyValue = props[propertyName] as Map<String, dynamic>;
-        if (propertyValue.containsKey(_allOfConst)) {
-          hasAllOfKey = true;
-        }
-      }
     }
 
     if (map case {_propertiesConst: final Map<String, dynamic> props}) {
@@ -820,7 +812,7 @@ class OpenApiParser {
           additionalName: additionalName,
           isRequired: (_apiInfo.schemaVersion == OAS.v2 && !config.useXNullable)
               ? isRequired
-              : isRequired || hasAllOfKey || hasDefaultKey,
+              : isRequired || hasDefaultKey,
         );
 
         var validation = propertyValue;
diff --git a/swagger_parser/test/e2e/tests/xof/all_of.3.0/expected_files/models/nullable_user_dto.dart b/swagger_parser/test/e2e/tests/xof/all_of.3.0/expected_files/models/nullable_user_dto.dart
index b2659722a..1711fcf99 100644
--- a/swagger_parser/test/e2e/tests/xof/all_of.3.0/expected_files/models/nullable_user_dto.dart
+++ b/swagger_parser/test/e2e/tests/xof/all_of.3.0/expected_files/models/nullable_user_dto.dart
@@ -12,7 +12,7 @@ part 'nullable_user_dto.g.dart';
 @Freezed()
 class NullableUserDto with _$NullableUserDto {
   const factory NullableUserDto({
-    @JsonKey(includeIfNull: true) required UserDto? data,
+    @JsonKey(includeIfNull: false) UserDto? data,
   }) = _NullableUserDto;
 
   factory NullableUserDto.fromJson(Map<String, Object?> json) =>
diff --git a/swagger_parser/test/parser/all_of_property_not_required_test.dart b/swagger_parser/test/parser/all_of_property_not_required_test.dart
new file mode 100644
index 000000000..8cc45162c
--- /dev/null
+++ b/swagger_parser/test/parser/all_of_property_not_required_test.dart
@@ -0,0 +1,100 @@
+import 'dart:io';
+
+import 'package:path/path.dart' as p;
+import 'package:swagger_parser/swagger_parser.dart';
+import 'package:test/test.dart';
+
+void main() {
+  test(
+    'properties not listed in required stay optional when a sibling uses allOf',
+    () async {
+      final root =
+          await Directory.systemTemp.createTemp('swagger-parser-test-');
+      addTearDown(() => root.delete(recursive: true));
+
+      final schema = File(p.join(root.path, 'openapi.yaml'))
+        ..writeAsStringSync(r'''
+openapi: 3.0.0
+info:
+  title: allOf properties without required
+  version: 1.0.0
+paths:
+  /foo:
+    get:
+      operationId: getFoo
+      responses:
+        '200':
+          description: OK
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Foo'
+  /order:
+    get:
+      operationId: getOrder
+      responses:
+        '200':
+          description: OK
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Order'
+components:
+  schemas:
+    Bar:
+      type: object
+      properties:
+        name:
+          type: string
+      required: [name]
+    Status:
+      type: string
+      enum: [active, inactive]
+    Foo:
+      type: object
+      # No required array: every property is optional.
+      properties:
+        a:
+          type: string
+        b:
+          allOf:
+            - $ref: '#/components/schemas/Bar'
+    Order:
+      type: object
+      # No required array: every property is optional.
+      properties:
+        id:
+          type: integer
+        status:
+          nullable: true
+          allOf:
+            - $ref: '#/components/schemas/Status'
+''');
+
+      await GenProcessor(
+        SWPConfig(
+          schemaPath: schema.path,
+          outputDirectory: p.join(root.path, 'generated'),
+          jsonSerializer: JsonSerializer.freezed,
+          putClientsInFolder: true,
+        ),
+      ).generateFiles();
+
+      final foo = File(
+        p.join(root.path, 'generated', 'models', 'foo.dart'),
+      ).readAsStringSync();
+      expect(foo, contains('String? a,'));
+      expect(foo, isNot(contains('required String? a')));
+      expect(foo, contains('Bar? b,'));
+      expect(foo, isNot(contains('required Bar? b')));
+
+      final order = File(
+        p.join(root.path, 'generated', 'models', 'order.dart'),
+      ).readAsStringSync();
+      expect(order, contains('int? id,'));
+      expect(order, isNot(contains('required int? id')));
+      expect(order, contains('Status? status,'));
+      expect(order, isNot(contains('required Status? status')));
+    },
+  );
+}