diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
index 56e5debcdcb5..904ee97303e1 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
@@ -2632,6 +2632,8 @@ protected void updateModelForComposedSchema(CodegenModel m, Schema schema, Map<S
 
         // TODO revise the logic below to set discriminator, xml attributes
         if (supportsInheritance || supportsMixins) {
+            // FIXME Comment out the next line, and allVars will be used in the template to generate the missing fields.
+            // Why is m.allVars being reset in this case?
             m.allVars = new ArrayList<>();
             if (composed.getAllOf() != null) {
                 int modelImplCnt = 0; // only one inline object allowed in a ComposedModel
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/kotlin/KotlinModelCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/kotlin/KotlinModelCodegenTest.java
index 59e42b4c1c01..d212680d3ab0 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/kotlin/KotlinModelCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/kotlin/KotlinModelCodegenTest.java
@@ -6,6 +6,7 @@
 import org.openapitools.codegen.ClientOptInput;
 import org.openapitools.codegen.CodegenConstants;
 import org.openapitools.codegen.DefaultGenerator;
+import org.openapitools.codegen.config.CodegenConfigurator;
 import org.openapitools.codegen.languages.AbstractKotlinCodegen;
 import org.openapitools.codegen.languages.KotlinClientCodegen;
 import org.openapitools.codegen.languages.KotlinServerCodegen;
@@ -110,4 +111,61 @@ public void mutableArrayWithUniqueItems(AbstractKotlinCodegen codegen) throws IO
         assertFileContains(Paths.get(outputPath + "/src/main/kotlin/models/UniqueArray.kt"),
                 "var array: kotlin.collections.MutableSet<kotlin.String>");
     }
+
+
+    private String generateModelsWIP(String inputFile) throws IOException {
+        KotlinClientCodegen codegen = new KotlinClientCodegen();
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+        codegen.setOutputDir(output.getAbsolutePath());
+        String outputPath = output.getAbsolutePath().replace('\\', '/');
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName("kotlin")
+                .setOutputDir(output.getAbsolutePath())
+                .setInputSpec(inputFile)
+                .addInlineSchemaOption("RESOLVE_INLINE_ENUMS", "true");
+        codegen.additionalProperties().put(CodegenConstants.MODEL_PACKAGE, "models");
+
+        DefaultGenerator generator = new DefaultGenerator();
+        generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
+        generator.setGeneratorPropertyDefault(CodegenConstants.MODEL_TESTS, "false");
+        generator.setGeneratorPropertyDefault(CodegenConstants.MODEL_DOCS, "false");
+        generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "false");
+        generator.setGeneratorPropertyDefault(CodegenConstants.SUPPORTING_FILES, "false");
+        generator.opts(configurator.toClientOptInput()).generate();
+        return outputPath;
+    }
+
+    @Test
+    public void dataClassGenerationNotWorkingWithAllOfInSchema() throws IOException {
+        String outputPath = generateModelsWIP("src/test/resources/3_1/issue_wip.yaml");
+
+        assertFileContains(Paths.get(outputPath + "/src/main/kotlin/org/openapitools/client/models/GetStuffFromPath200ResponseInner.kt"),
+                "val aBooleanCheck: kotlin.Boolean? = null,",
+                "val condition: kotlin.String? = null,",
+                "val purpose: kotlin.collections.List<GetStuffFromPath200ResponseInnerPurposeInner>? = null"
+        );
+        assertFileContains(Paths.get(outputPath + "/src/main/kotlin/org/openapitools/client/models/GetStuffFromPath200ResponseInnerPurposeInner.kt"),
+                "FIRST(\"FIRST\"),",
+                "SECOND(\"SECOND\"),",
+                "THIRD(\"THIRD\");"
+        );
+    }
+
+    @Test
+    public void dataClassGenerationWorkingWithoutAllOfInSchema() throws IOException {
+
+       String outputPath = generateModelsWIP("src/test/resources/3_1/issue_wip_working_without_all_of.yaml");
+
+        assertFileContains(Paths.get(outputPath + "/src/main/kotlin/org/openapitools/client/models/GetStuffFromPath200ResponseInner.kt"),
+                "val aBooleanCheck: kotlin.Boolean? = null,",
+                "val condition: kotlin.String? = null,",
+                "val purpose: kotlin.collections.List<GetStuffFromPath200ResponseInnerPurposeInner>? = null"
+        );
+        assertFileContains(Paths.get(outputPath + "/src/main/kotlin/org/openapitools/client/models/GetStuffFromPath200ResponseInnerPurposeInner.kt"),
+                "FIRST(\"FIRST\"),",
+                "SECOND(\"SECOND\"),",
+                "THIRD(\"THIRD\");"
+        );
+    }
 }
diff --git a/modules/openapi-generator/src/test/resources/3_1/issue_wip.yaml b/modules/openapi-generator/src/test/resources/3_1/issue_wip.yaml
new file mode 100644
index 000000000000..913c0eae470b
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_1/issue_wip.yaml
@@ -0,0 +1,51 @@
+openapi: 3.1.0
+info:
+  title: Title
+  description: Description
+  version: 1.0.0
+servers:
+  - url: /
+paths:
+  /v1/path:
+    get:
+      summary: A path
+      description: Stuff happens on this path
+      operationId: getStuffFromPath
+      responses:
+        "200":
+          description: OK
+          content:
+            application/json:
+              schema:
+                type: array
+                title: AListOfThings
+                items:
+                  type: object
+                  allOf:
+                    - if:
+                        properties:
+                          aBooleanCheck:
+                            const: false
+                      then:
+                        required:
+                          - condition
+                    - if:
+                        properties:
+                          aBooleanCheck:
+                            const: true
+                      then:
+                        required:
+                          - purpose
+                  properties:
+                    aBooleanCheck:
+                      type: boolean
+                    condition:
+                      type: string
+                    purpose:
+                      type: array
+                      items:
+                        type: string
+                        enum:
+                          - FIRST
+                          - SECOND
+                          - THIRD
\ No newline at end of file
diff --git a/modules/openapi-generator/src/test/resources/3_1/issue_wip_working_without_all_of.yaml b/modules/openapi-generator/src/test/resources/3_1/issue_wip_working_without_all_of.yaml
new file mode 100644
index 000000000000..b93c8fde5223
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_1/issue_wip_working_without_all_of.yaml
@@ -0,0 +1,36 @@
+openapi: 3.1.0
+info:
+  title: Title
+  description: Description
+  version: 1.0.0
+servers:
+  - url: /
+paths:
+  /v1/path:
+    get:
+      summary: A path
+      description: Stuff happens on this path
+      operationId: getStuffFromPath
+      responses:
+        "200":
+          description: OK
+          content:
+            application/json:
+              schema:
+                type: array
+                title: AListOfThings
+                items:
+                  type: object
+                  properties:
+                    aBooleanCheck:
+                      type: boolean
+                    condition:
+                      type: string
+                    purpose:
+                      type: array
+                      items:
+                        type: string
+                        enum:
+                          - FIRST
+                          - SECOND
+                          - THIRD
\ No newline at end of file