diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenParameter.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenParameter.java
index eb6522a93189..d290aa5c6abd 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenParameter.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenParameter.java
@@ -41,6 +41,7 @@ public class CodegenParameter {
     public CodegenProperty mostInnerItems;
     public Map<String, Object> vendorExtensions = new HashMap<String, Object>();
     public boolean hasValidation;
+    public boolean isNullable;
 
     /**
      * Determines whether this parameter is mandatory. If the parameter is in "path",
@@ -150,6 +151,7 @@ public CodegenParameter copy() {
             output.vendorExtensions = new HashMap<String, Object>(this.vendorExtensions);
         }
         output.hasValidation = this.hasValidation;
+        output.isNullable = this.isNullable;
         output.isBinary = this.isBinary;
         output.isByteArray = this.isByteArray;
         output.isString = this.isString;
@@ -269,6 +271,8 @@ public boolean equals(Object o) {
             return false;
         if (hasValidation != that.hasValidation)
             return false;
+        if (isNullable != that.isNullable)
+            return false;
         if (required != that.required)
             return false;
         if (maximum != null ? !maximum.equals(that.maximum) : that.maximum != null)
@@ -344,6 +348,7 @@ public int hashCode() {
         result = 31 * result + (mostInnerItems != null ? mostInnerItems.hashCode() : 0);
         result = 31 * result + (vendorExtensions != null ? vendorExtensions.hashCode() : 0);
         result = 31 * result + (hasValidation ? 13:31);
+        result = 31 * result + (isNullable ? 13:31);
         result = 31 * result + (required ? 13:31);
         result = 31 * result + (maximum != null ? maximum.hashCode() : 0);
         result = 31 * result + (exclusiveMaximum ? 13:31);
@@ -409,6 +414,7 @@ public java.lang.String toString() {
                 ", mostInnerItems=" + mostInnerItems +
                 ", vendorExtensions=" + vendorExtensions +
                 ", hasValidation=" + hasValidation +
+                ", isNullable=" + isNullable +
                 ", required=" + required +
                 ", maximum='" + maximum + '\'' +
                 ", exclusiveMaximum=" + exclusiveMaximum +
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 61d1ae831552..01017af3fad7 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
@@ -1789,7 +1789,11 @@ public CodegenProperty fromProperty(String name, Schema p) {
         if (p.getWriteOnly() != null) {
             property.isWriteOnly = p.getWriteOnly();
         }
-        if (p.getNullable() != null) {
+
+        // use x-nullable
+        if (p.getExtensions() != null && p.getExtensions().get("x-nullable") != null) {
+            property.isNullable = Boolean.valueOf(p.getExtensions().get("x-nullable").toString());
+        } else if (p.getNullable() != null) { // use nullable defined in OAS3
             property.isNullable = p.getNullable();
         }
 
@@ -2649,6 +2653,14 @@ public CodegenParameter fromParameter(Parameter parameter, Set<String> imports)
                 LOGGER.warn("warning!  Schema not found for parameter \"" + parameter.getName() + "\", using String");
                 parameterSchema = new StringSchema().description("//TODO automatically added by openapi-generator due to missing type definition.");
             }
+
+            // x-nullable extension in OAS2
+            if (parameter.getExtensions() != null && parameter.getExtensions().get("x-nullable") != null) {
+                codegenParameter.isNullable = Boolean.valueOf(parameter.getExtensions().get("x-nullable").toString());
+            } else if (Boolean.TRUE.equals(parameterSchema.getNullable())) { // use nullable defined in the spec
+                codegenParameter.isNullable = true;
+            }
+
             // set default value
             if (parameterSchema.getDefault() != null) {
                 codegenParameter.defaultValue = toDefaultValue(parameterSchema);
@@ -4265,6 +4277,9 @@ public List<CodegenParameter> fromRequestBodyToFormParameters(RequestBody body,
                     // default to csv:
                     codegenParameter.collectionFormat = StringUtils.isEmpty(collectionFormat) ? "csv" : collectionFormat;
 
+                    // set nullable
+                    setParameterNullable(codegenParameter, codegenProperty);
+
                     // recursively add import
                     while (codegenProperty != null) {
                         imports.add(codegenProperty.baseType);
@@ -4293,7 +4308,7 @@ public List<CodegenParameter> fromRequestBodyToFormParameters(RequestBody body,
     public CodegenParameter fromFormProperty(String name, Schema propertySchema, Set<String> imports) {
         CodegenParameter codegenParameter = CodegenModelFactory.newInstance(CodegenModelType.PARAMETER);
 
-        LOGGER.debug("Debugging fromFormProperty: " + name);
+        LOGGER.debug("Debugging fromFormProperty {}: {}", name, propertySchema);
         CodegenProperty codegenProperty = fromProperty(name, propertySchema);
 
         codegenParameter.isFormParam = Boolean.TRUE;
@@ -4307,7 +4322,6 @@ public CodegenParameter fromFormProperty(String name, Schema propertySchema, Set
         codegenParameter.jsonSchema = Json.pretty(propertySchema);
         codegenParameter.defaultValue = codegenProperty.getDefaultValue();
 
-
         if (codegenProperty.getVendorExtensions() != null && !codegenProperty.getVendorExtensions().isEmpty()) {
             codegenParameter.vendorExtensions = codegenProperty.getVendorExtensions();
         }
@@ -4366,6 +4380,8 @@ public CodegenParameter fromFormProperty(String name, Schema propertySchema, Set
 
         setParameterBooleanFlagWithCodegenProperty(codegenParameter, codegenProperty);
         setParameterExampleValue(codegenParameter);
+        // set nullable
+        setParameterNullable(codegenParameter, codegenProperty);
 
         //TODO collectionFormat for form parameter not yet supported
         //codegenParameter.collectionFormat = getCollectionFormat(propertySchema);
@@ -4415,6 +4431,9 @@ public CodegenParameter fromRequestBody(RequestBody body, Map<String, Schema> sc
             codegenParameter.isMapContainer = Boolean.TRUE;
 
             setParameterBooleanFlagWithCodegenProperty(codegenParameter, codegenProperty);
+
+            // set nullable
+            setParameterNullable(codegenParameter, codegenProperty);
         } else if (ModelUtils.isArraySchema(schema)) {
             final ArraySchema arraySchema = (ArraySchema) schema;
             Schema inner = arraySchema.getItems();
@@ -4454,6 +4473,8 @@ public CodegenParameter fromRequestBody(RequestBody body, Map<String, Schema> sc
             codegenParameter.isListContainer = Boolean.TRUE;
 
             setParameterBooleanFlagWithCodegenProperty(codegenParameter, codegenProperty);
+            // set nullable
+            setParameterNullable(codegenParameter, codegenProperty);
 
             while (codegenProperty != null) {
                 imports.add(codegenProperty.baseType);
@@ -4516,6 +4537,8 @@ public CodegenParameter fromRequestBody(RequestBody body, Map<String, Schema> sc
                     }
                 }
                 setParameterBooleanFlagWithCodegenProperty(codegenParameter, codegenProperty);
+                // set nullable
+                setParameterNullable(codegenParameter, codegenProperty);
             }
 
         } else {
@@ -4539,6 +4562,8 @@ public CodegenParameter fromRequestBody(RequestBody body, Map<String, Schema> sc
 
             }
             setParameterBooleanFlagWithCodegenProperty(codegenParameter, codegenProperty);
+            // set nullable
+            setParameterNullable(codegenParameter, codegenProperty);
         }
 
         // set the parameter's example value
@@ -4636,4 +4661,12 @@ public List<CodegenServerVariable> fromServerVariables(Map<String, ServerVariabl
         }
         return codegenServerVariables;
     }
+
+    private void setParameterNullable(CodegenParameter parameter, CodegenProperty property) {
+        if (property.getVendorExtensions() != null && property.getVendorExtensions().get("x-nullable") != null) {
+            parameter.isNullable = Boolean.valueOf(property.getVendorExtensions().get("x-nullable").toString());
+        } else {
+            parameter.isNullable = property.isNullable;
+        }
+    }
 }
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/ruby/RubyClientCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/ruby/RubyClientCodegenTest.java
index a0c5a326ead1..2e43257eaa26 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/ruby/RubyClientCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/ruby/RubyClientCodegenTest.java
@@ -172,7 +172,7 @@ public void bodyParameterTest() {
 
 
     @Test(description = "test nullable for properties")
-    public void nullableTest() {
+    public void nullablePropertyTest() {
         final OpenAPI openAPI = new OpenAPIParser().readLocation("src/test/resources/3_0/petstore_oas3_test.yaml", null, new ParseOptions()).getOpenAPI();
         final RubyClientCodegen codegen = new RubyClientCodegen();
         codegen.setModuleName("OnlinePetstore");
@@ -227,4 +227,49 @@ public void propertiesWithoutNullableTest() {
         Assert.assertFalse(cp5.isNullable);
     }
 
+    @Test(description = "test nullable for parameters (OAS3)")
+    public void nullableParameterOAS3Test() {
+        final OpenAPI openAPI = new OpenAPIParser().readLocation("src/test/resources/3_0/petstore_oas3_test.yaml", null, new ParseOptions()).getOpenAPI();
+        final RubyClientCodegen codegen = new RubyClientCodegen();
+        codegen.setModuleName("OnlinePetstore");
+        final String path = "/pet/{petId}";
+
+        final Operation p = openAPI.getPaths().get(path).getPost();
+        final CodegenOperation op = codegen.fromOperation(path, "post", p, openAPI.getComponents().getSchemas());
+
+        Assert.assertEquals(op.pathParams.size(), 1);
+        CodegenParameter pp = op.pathParams.get(0);
+        Assert.assertTrue(pp.isNullable);
+
+        Assert.assertEquals(op.formParams.size(), 2);
+        CodegenParameter name = op.formParams.get(0);
+        Assert.assertFalse(name.isNullable);
+        CodegenParameter status = op.formParams.get(1);
+        Assert.assertTrue(status.isNullable);
+    }
+
+    @Test(description = "test nullable for parameters (OAS2)")
+    public void nullableParameterOAS2Test() {
+        final OpenAPI openAPI = new OpenAPIParser().readLocation("src/test/resources/2_0/petstore-nullable.yaml", null, new ParseOptions()).getOpenAPI();
+        final RubyClientCodegen codegen = new RubyClientCodegen();
+        codegen.setModuleName("OnlinePetstore");
+        final String path = "/pet/{petId}";
+
+        final Operation p = openAPI.getPaths().get(path).getPost();
+        final CodegenOperation op = codegen.fromOperation(path, "post", p, openAPI.getComponents().getSchemas());
+
+        // path parameter x-nullable test
+        Assert.assertEquals(op.pathParams.size(), 1);
+        CodegenParameter pp = op.pathParams.get(0);
+        Assert.assertTrue(pp.isNullable);
+
+        // form parameter x-nullable test
+        Assert.assertEquals(op.formParams.size(), 2);
+        CodegenParameter name = op.formParams.get(0);
+        Assert.assertFalse(name.isNullable);
+        CodegenParameter status = op.formParams.get(1);
+        // TODO comment out the following as there seems to be an issue with swagger parser not brining over the
+        // vendor extensions of the form parameter when creating the schema
+        //Assert.assertTrue(status.isNullable);
+    }
 }
diff --git a/modules/openapi-generator/src/test/resources/2_0/petstore-nullable.yaml b/modules/openapi-generator/src/test/resources/2_0/petstore-nullable.yaml
new file mode 100644
index 000000000000..cff13ed73ce4
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/2_0/petstore-nullable.yaml
@@ -0,0 +1,702 @@
+swagger: '2.0'
+info:
+  description: 'This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.'
+  version: 1.0.0
+  title: OpenAPI Petstore
+  license:
+    name: Apache-2.0
+    url: 'http://www.apache.org/licenses/LICENSE-2.0.html'
+host: petstore.swagger.io
+basePath: /v2
+tags:
+  - name: pet
+    description: Everything about your Pets
+  - name: store
+    description: Access to Petstore orders
+  - name: user
+    description: Operations about user
+schemes:
+  - http
+paths:
+  /pet:
+    post:
+      tags:
+        - pet
+      summary: Add a new pet to the store
+      description: ''
+      operationId: addPet
+      consumes:
+        - application/json
+        - application/xml
+      produces:
+        - application/xml
+        - application/json
+      parameters:
+        - in: body
+          name: body
+          description: Pet object that needs to be added to the store
+          required: true
+          schema:
+            $ref: '#/definitions/Pet'
+      responses:
+        '405':
+          description: Invalid input
+      security:
+        - petstore_auth:
+            - 'write:pets'
+            - 'read:pets'
+    put:
+      tags:
+        - pet
+      summary: Update an existing pet
+      description: ''
+      operationId: updatePet
+      consumes:
+        - application/json
+        - application/xml
+      produces:
+        - application/xml
+        - application/json
+      parameters:
+        - in: body
+          name: body
+          description: Pet object that needs to be added to the store
+          required: true
+          schema:
+            $ref: '#/definitions/Pet'
+      responses:
+        '400':
+          description: Invalid ID supplied
+        '404':
+          description: Pet not found
+        '405':
+          description: Validation exception
+      security:
+        - petstore_auth:
+            - 'write:pets'
+            - 'read:pets'
+  /pet/findByStatus:
+    get:
+      tags:
+        - pet
+      summary: Finds Pets by status
+      description: Multiple status values can be provided with comma separated strings
+      operationId: findPetsByStatus
+      produces:
+        - application/xml
+        - application/json
+      parameters:
+        - name: status
+          in: query
+          description: Status values that need to be considered for filter
+          required: true
+          type: array
+          items:
+            type: string
+            enum:
+              - available
+              - pending
+              - sold
+            default: available
+          collectionFormat: csv
+      responses:
+        '200':
+          description: successful operation
+          schema:
+            type: array
+            items:
+              $ref: '#/definitions/Pet'
+        '400':
+          description: Invalid status value
+      security:
+        - petstore_auth:
+            - 'write:pets'
+            - 'read:pets'
+  /pet/findByTags:
+    get:
+      tags:
+        - pet
+      summary: Finds Pets by tags
+      description: 'Multiple tags can be provided with comma separated strings. Use tag1, tag2, tag3 for testing.'
+      operationId: findPetsByTags
+      produces:
+        - application/xml
+        - application/json
+      parameters:
+        - name: tags
+          in: query
+          description: Tags to filter by
+          required: true
+          type: array
+          items:
+            type: string
+          collectionFormat: csv
+      responses:
+        '200':
+          description: successful operation
+          schema:
+            type: array
+            items:
+              $ref: '#/definitions/Pet'
+        '400':
+          description: Invalid tag value
+      security:
+        - petstore_auth:
+            - 'write:pets'
+            - 'read:pets'
+      deprecated: true
+  '/pet/{petId}':
+    get:
+      tags:
+        - pet
+      summary: Find pet by ID
+      description: Returns a single pet
+      operationId: getPetById
+      produces:
+        - application/xml
+        - application/json
+      parameters:
+        - name: petId
+          in: path
+          description: ID of pet to return
+          required: true
+          type: integer
+          format: int64
+      responses:
+        '200':
+          description: successful operation
+          schema:
+            $ref: '#/definitions/Pet'
+        '400':
+          description: Invalid ID supplied
+        '404':
+          description: Pet not found
+      security:
+        - api_key: []
+    post:
+      tags:
+        - pet
+      summary: Updates a pet in the store with form data
+      description: ''
+      operationId: updatePetWithForm
+      consumes:
+        - application/x-www-form-urlencoded
+      produces:
+        - application/xml
+        - application/json
+      parameters:
+        - name: petId
+          in: path
+          description: ID of pet that needs to be updated
+          required: true
+          type: integer
+          format: int64
+          x-nullable: true
+        - name: name
+          in: formData
+          description: Updated name of the pet
+          required: false
+          type: string
+        - name: status
+          in: formData
+          description: Updated status of the pet
+          required: false
+          type: string
+          x-nullable: true
+      responses:
+        '405':
+          description: Invalid input
+      security:
+        - petstore_auth:
+            - 'write:pets'
+            - 'read:pets'
+    delete:
+      tags:
+        - pet
+      summary: Deletes a pet
+      description: ''
+      operationId: deletePet
+      produces:
+        - application/xml
+        - application/json
+      parameters:
+        - name: api_key
+          in: header
+          required: false
+          type: string
+        - name: petId
+          in: path
+          description: Pet id to delete
+          required: true
+          type: integer
+          format: int64
+      responses:
+        '400':
+          description: Invalid pet value
+      security:
+        - petstore_auth:
+            - 'write:pets'
+            - 'read:pets'
+  '/pet/{petId}/uploadImage':
+    post:
+      tags:
+        - pet
+      summary: uploads an image
+      description: ''
+      operationId: uploadFile
+      consumes:
+        - multipart/form-data
+      produces:
+        - application/json
+      parameters:
+        - name: petId
+          in: path
+          description: ID of pet to update
+          required: true
+          type: integer
+          format: int64
+        - name: additionalMetadata
+          in: formData
+          description: Additional data to pass to server
+          required: false
+          type: string
+        - name: file
+          in: formData
+          description: file to upload
+          required: false
+          type: file
+      responses:
+        '200':
+          description: successful operation
+          schema:
+            $ref: '#/definitions/ApiResponse'
+      security:
+        - petstore_auth:
+            - 'write:pets'
+            - 'read:pets'
+  /store/inventory:
+    get:
+      tags:
+        - store
+      summary: Returns pet inventories by status
+      description: Returns a map of status codes to quantities
+      operationId: getInventory
+      produces:
+        - application/json
+      parameters: []
+      responses:
+        '200':
+          description: successful operation
+          schema:
+            type: object
+            additionalProperties:
+              type: integer
+              format: int32
+      security:
+        - api_key: []
+  /store/order:
+    post:
+      tags:
+        - store
+      summary: Place an order for a pet
+      description: ''
+      operationId: placeOrder
+      produces:
+        - application/xml
+        - application/json
+      parameters:
+        - in: body
+          name: body
+          description: order placed for purchasing the pet
+          required: true
+          schema:
+            $ref: '#/definitions/Order'
+      responses:
+        '200':
+          description: successful operation
+          schema:
+            $ref: '#/definitions/Order'
+        '400':
+          description: Invalid Order
+  '/store/order/{orderId}':
+    get:
+      tags:
+        - store
+      summary: Find purchase order by ID
+      description: 'For valid response try integer IDs with value <= 5 or > 10. Other values will generated exceptions'
+      operationId: getOrderById
+      produces:
+        - application/xml
+        - application/json
+      parameters:
+        - name: orderId
+          in: path
+          description: ID of pet that needs to be fetched
+          required: true
+          type: integer
+          maximum: 5
+          minimum: 1
+          format: int64
+      responses:
+        '200':
+          description: successful operation
+          schema:
+            $ref: '#/definitions/Order'
+        '400':
+          description: Invalid ID supplied
+        '404':
+          description: Order not found
+    delete:
+      tags:
+        - store
+      summary: Delete purchase order by ID
+      description: For valid response try integer IDs with value < 1000. Anything above 1000 or nonintegers will generate API errors
+      operationId: deleteOrder
+      produces:
+        - application/xml
+        - application/json
+      parameters:
+        - name: orderId
+          in: path
+          description: ID of the order that needs to be deleted
+          required: true
+          type: string
+      responses:
+        '400':
+          description: Invalid ID supplied
+        '404':
+          description: Order not found
+  /user:
+    post:
+      tags:
+        - user
+      summary: Create user
+      description: This can only be done by the logged in user.
+      operationId: createUser
+      produces:
+        - application/xml
+        - application/json
+      parameters:
+        - in: body
+          name: body
+          description: Created user object
+          required: true
+          schema:
+            $ref: '#/definitions/User'
+      responses:
+        default:
+          description: successful operation
+  /user/createWithArray:
+    post:
+      tags:
+        - user
+      summary: Creates list of users with given input array
+      description: ''
+      operationId: createUsersWithArrayInput
+      produces:
+        - application/xml
+        - application/json
+      parameters:
+        - in: body
+          name: body
+          description: List of user object
+          required: true
+          schema:
+            type: array
+            items:
+              $ref: '#/definitions/User'
+      responses:
+        default:
+          description: successful operation
+  /user/createWithList:
+    post:
+      tags:
+        - user
+      summary: Creates list of users with given input array
+      description: ''
+      operationId: createUsersWithListInput
+      produces:
+        - application/xml
+        - application/json
+      parameters:
+        - in: body
+          name: body
+          description: List of user object
+          required: true
+          schema:
+            type: array
+            items:
+              $ref: '#/definitions/User'
+      responses:
+        default:
+          description: successful operation
+  /user/login:
+    get:
+      tags:
+        - user
+      summary: Logs user into the system
+      description: ''
+      operationId: loginUser
+      produces:
+        - application/xml
+        - application/json
+      parameters:
+        - name: username
+          in: query
+          description: The user name for login
+          required: true
+          type: string
+        - name: password
+          in: query
+          description: The password for login in clear text
+          required: true
+          type: string
+      responses:
+        '200':
+          description: successful operation
+          schema:
+            type: string
+          headers:
+            X-Rate-Limit:
+              type: integer
+              format: int32
+              description: calls per hour allowed by the user
+            X-Expires-After:
+              type: string
+              format: date-time
+              description: date in UTC when toekn expires
+        '400':
+          description: Invalid username/password supplied
+  /user/logout:
+    get:
+      tags:
+        - user
+      summary: Logs out current logged in user session
+      description: ''
+      operationId: logoutUser
+      produces:
+        - application/xml
+        - application/json
+      parameters: []
+      responses:
+        default:
+          description: successful operation
+  '/user/{username}':
+    get:
+      tags:
+        - user
+      summary: Get user by user name
+      description: ''
+      operationId: getUserByName
+      produces:
+        - application/xml
+        - application/json
+      parameters:
+        - name: username
+          in: path
+          description: 'The name that needs to be fetched. Use user1 for testing.'
+          required: true
+          type: string
+      responses:
+        '200':
+          description: successful operation
+          schema:
+            $ref: '#/definitions/User'
+        '400':
+          description: Invalid username supplied
+        '404':
+          description: User not found
+    put:
+      tags:
+        - user
+      summary: Updated user
+      description: This can only be done by the logged in user.
+      operationId: updateUser
+      produces:
+        - application/xml
+        - application/json
+      parameters:
+        - name: username
+          in: path
+          description: name that need to be deleted
+          required: true
+          type: string
+        - in: body
+          name: body
+          description: Updated user object
+          required: true
+          schema:
+            $ref: '#/definitions/User'
+      responses:
+        '400':
+          description: Invalid user supplied
+        '404':
+          description: User not found
+    delete:
+      tags:
+        - user
+      summary: Delete user
+      description: This can only be done by the logged in user.
+      operationId: deleteUser
+      produces:
+        - application/xml
+        - application/json
+      parameters:
+        - name: username
+          in: path
+          description: The name that needs to be deleted
+          required: true
+          type: string
+      responses:
+        '400':
+          description: Invalid username supplied
+        '404':
+          description: User not found
+securityDefinitions:
+  petstore_auth:
+    type: oauth2
+    authorizationUrl: 'http://petstore.swagger.io/api/oauth/dialog'
+    flow: implicit
+    scopes:
+      'write:pets': modify pets in your account
+      'read:pets': read your pets
+  api_key:
+    type: apiKey
+    name: api_key
+    in: header
+definitions:
+  Order:
+    title: Pet Order
+    description: An order for a pets from the pet store
+    type: object
+    properties:
+      id:
+        type: integer
+        format: int64
+      petId:
+        type: integer
+        format: int64
+      quantity:
+        type: integer
+        format: int32
+      shipDate:
+        type: string
+        format: date-time
+      status:
+        type: string
+        description: Order Status
+        enum:
+          - placed
+          - approved
+          - delivered
+      complete:
+        type: boolean
+        default: false
+    xml:
+      name: Order
+  Category:
+    title: Pet category
+    description: A category for a pet
+    type: object
+    properties:
+      id:
+        type: integer
+        format: int64
+      name:
+        type: string
+    xml:
+      name: Category
+  User:
+    title: a User
+    description: A User who is purchasing from the pet store
+    type: object
+    properties:
+      id:
+        type: integer
+        format: int64
+      username:
+        type: string
+      firstName:
+        type: string
+      lastName:
+        type: string
+      email:
+        type: string
+      password:
+        type: string
+      phone:
+        type: string
+      userStatus:
+        type: integer
+        format: int32
+        description: User Status
+    xml:
+      name: User
+  Tag:
+    title: Pet Tag
+    description: A tag for a pet
+    type: object
+    properties:
+      id:
+        type: integer
+        format: int64
+      name:
+        type: string
+    xml:
+      name: Tag
+  Pet:
+    title: a Pet
+    description: A pet for sale in the pet store
+    type: object
+    required:
+      - name
+      - photoUrls
+    properties:
+      id:
+        type: integer
+        format: int64
+        x-nullable: true
+      category:
+        $ref: '#/definitions/Category'
+      name:
+        type: string
+        example: doggie
+        x-nullable: true
+      photoUrls:
+        type: array
+        xml:
+          name: photoUrl
+          wrapped: true
+        items:
+          type: string
+          x-nullable: true
+      tags:
+        x-nullable: true
+        type: array
+        xml:
+          name: tag
+          wrapped: true
+        items:
+          $ref: '#/definitions/Tag'
+      status:
+        type: string
+        x-nullable: true
+        description: pet status in the store
+        enum:
+          - available
+          - pending
+          - sold
+    xml:
+      name: Pet
+  ApiResponse:
+    title: An uploaded response
+    description: Describes the result of uploading an image resource
+    type: object
+    properties:
+      code:
+        type: integer
+        format: int32
+      type:
+        type: string
+      message:
+        type: string
diff --git a/modules/openapi-generator/src/test/resources/3_0/petstore_oas3_test.yaml b/modules/openapi-generator/src/test/resources/3_0/petstore_oas3_test.yaml
index c9c83e09a6be..370ae3ee32f6 100644
--- a/modules/openapi-generator/src/test/resources/3_0/petstore_oas3_test.yaml
+++ b/modules/openapi-generator/src/test/resources/3_0/petstore_oas3_test.yaml
@@ -181,6 +181,7 @@ paths:
           schema:
             type: integer
             format: int64
+            nullable: true
       responses:
         '405':
           description: Invalid input
@@ -200,6 +201,7 @@ paths:
                 status:
                   description: Updated status of the pet
                   type: string
+                  nullable: true
     delete:
       tags:
         - pet