diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenProperty.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenProperty.java
index 8631b2cbaed9..92475f1ac046 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenProperty.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenProperty.java
@@ -134,7 +134,9 @@ public class CodegenProperty implements Cloneable, IJsonSchemaValidationProperti
     public boolean isUri;
     public boolean isEmail;
     /**
-     * The type is a free-form object, i.e. it is a map of string to values with no declared properties
+     * The type is a free-form object, i.e. it is a map of string to values with no declared properties.
+     * A OAS free-form schema may include the 'additionalProperties' attribute, which puts a constraint
+     * on the type of the undeclared properties.
      */
     public boolean isFreeFormObject;
     /**
@@ -153,6 +155,9 @@ public class CodegenProperty implements Cloneable, IJsonSchemaValidationProperti
     public boolean isDiscriminator;
     public List<String> _enum;
     public Map<String, Object> allowableValues;
+    // If 'additionalProperties' is not set, items is null.
+    // If 'additionalProperties' is set to a type or refers to a type, 'items' provides the type information for
+    // the undeclared properties. 
     public CodegenProperty items;
     public CodegenProperty mostInnerItems;
     public Map<String, Object> vendorExtensions = new HashMap<String, Object>();
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 68919c695a06..b3d02767d03d 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
@@ -2180,7 +2180,14 @@ public CodegenModel fromModel(String name, Schema schema) {
             m.xmlNamespace = schema.getXml().getNamespace();
             m.xmlName = schema.getXml().getName();
         }
-
+        if (ModelUtils.isAnyTypeSchema(schema)) {
+            // The 'null' value is allowed when the OAS schema is 'any type'.
+            // See https://github.com/OAI/OpenAPI-Specification/issues/1389
+            if (Boolean.FALSE.equals(schema.getNullable())) {
+                LOGGER.error("Schema '{}' is any type, which includes the 'null' value. 'nullable' cannot be set to 'false'", name);
+            }
+            m.isNullable = true;
+        }
         if (ModelUtils.isArraySchema(schema)) {
             m.isArrayModel = true;
             m.arrayModelType = fromProperty(name, schema).complexType;
@@ -3030,6 +3037,12 @@ public CodegenProperty fromProperty(String name, Schema p) {
         } else if (ModelUtils.isFreeFormObject(p)) {
             property.isFreeFormObject = true;
         } else if (ModelUtils.isAnyTypeSchema(p)) {
+            // The 'null' value is allowed when the OAS schema is 'any type'.
+            // See https://github.com/OAI/OpenAPI-Specification/issues/1389
+            if (Boolean.FALSE.equals(p.getNullable())) {
+                LOGGER.warn("Schema '{}' is any type, which includes the 'null' value. 'nullable' cannot be set to 'false'", p.getName());
+            }
+            property.isNullable = true;
             property.isAnyType = true;
         } else if (ModelUtils.isArraySchema(p)) {
             // default to string if inner item is undefined
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientCodegen.java
index 74796111afd9..a7e186c3735a 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientCodegen.java
@@ -143,6 +143,7 @@ public PythonClientCodegen() {
         // map uuid to string for the time being
         typeMapping.put("UUID", "str");
         typeMapping.put("URI", "str");
+        typeMapping.put("null", "none_type");
 
         // from https://docs.python.org/3/reference/lexical_analysis.html#keywords
         setReservedWordsLowerCase(
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientExperimentalCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientExperimentalCodegen.java
index 4a946a0c84b4..92c76bb89bbb 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientExperimentalCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientExperimentalCodegen.java
@@ -388,7 +388,9 @@ public Map<String, Object> postProcessAllModels(Map<String, Object> objs) {
                 composedSchemaSets.add(cm.oneOf);
                 for (Set<String> importSet : composedSchemaSets) {
                     for (String otherModelName : importSet) {
-                        cm.imports.add(otherModelName);
+                        if (!languageSpecificPrimitives.contains(otherModelName)) {
+                            cm.imports.add(otherModelName);
+                        }
                     }
                 }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/OneOfImplementorAdditionalData.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/OneOfImplementorAdditionalData.java
index c44c2134d141..3ba31200598c 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/OneOfImplementorAdditionalData.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/OneOfImplementorAdditionalData.java
@@ -75,9 +75,11 @@ public void addFromInterfaceModel(CodegenModel cm, List<Map<String, String>> mod
         // note that we can't just toAdd.removeAll(m.vars) for every interfaceModel,
         // as they might have different value of `hasMore` and thus are not equal
         List<String> omitAdding = new ArrayList<String>();
-        for (CodegenModel m : cm.interfaceModels) {
-            for (CodegenProperty v : m.vars) {
-                omitAdding.add(v.baseName);
+        if (cm.interfaceModels != null) {
+            for (CodegenModel m : cm.interfaceModels) {
+                for (CodegenProperty v : m.vars) {
+                    omitAdding.add(v.baseName);
+                }
             }
         }
         for (CodegenProperty v : toAdd) {
diff --git a/modules/openapi-generator/src/main/resources/python/python-experimental/model_utils.mustache b/modules/openapi-generator/src/main/resources/python/python-experimental/model_utils.mustache
index 9111fcb830b8..fcbb59e79151 100644
--- a/modules/openapi-generator/src/main/resources/python/python-experimental/model_utils.mustache
+++ b/modules/openapi-generator/src/main/resources/python/python-experimental/model_utils.mustache
@@ -1153,7 +1153,7 @@ def get_oneof_instance(self, model_args, constant_args):
             and path to item.
 
     Returns
-        oneof_instance (instance/None)
+        oneof_instance (instance)
     """
     if len(self._composed_schemas['oneOf']) == 0:
         return None
@@ -1162,6 +1162,13 @@ def get_oneof_instance(self, model_args, constant_args):
     # Iterate over each oneOf schema and determine if the input data
     # matches the oneOf schemas.
     for oneof_class in self._composed_schemas['oneOf']:
+        # The composed oneOf schema allows the 'null' type and the input data
+        # is the null value. This is a OAS >= 3.1 feature.
+        if oneof_class is none_type:
+            # skip none_types because we are deserializing dict data.
+            # none_type deserialization is handled in the __new__ method
+            continue
+
         # transform js keys from input data to python keys in fixed_model_args
         fixed_model_args = change_keys_js_to_python(
             model_args, oneof_class)
@@ -1207,9 +1214,11 @@ def get_anyof_instances(self, model_args, constant_args):
     Args:
         self: the class we are handling
         model_args (dict): var_name to var_value
-            used to make instances
+            The input data, e.g. the payload that must match at least one
+            anyOf child schema in the OpenAPI document.
         constant_args (dict): var_name to var_value
-            used to make instances
+            args that every model requires, including configuration, server
+            and path to item.
 
     Returns
         anyof_instances (list)
@@ -1219,6 +1228,13 @@ def get_anyof_instances(self, model_args, constant_args):
         return anyof_instances
 
     for anyof_class in self._composed_schemas['anyOf']:
+        # The composed oneOf schema allows the 'null' type and the input data
+        # is the null value. This is a OAS >= 3.1 feature.
+        if anyof_class is none_type:
+            # skip none_types because we are deserializing dict data.
+            # none_type deserialization is handled in the __new__ method
+            continue
+
         # transform js keys to python keys in fixed_model_args
         fixed_model_args = change_keys_js_to_python(model_args, anyof_class)
 
diff --git a/modules/openapi-generator/src/test/resources/3_0/python-experimental/petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml b/modules/openapi-generator/src/test/resources/3_0/python-experimental/petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml
index 919bcc7445e9..edc4ca0e641e 100644
--- a/modules/openapi-generator/src/test/resources/3_0/python-experimental/petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml
+++ b/modules/openapi-generator/src/test/resources/3_0/python-experimental/petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml
@@ -1250,22 +1250,32 @@ components:
           type: integer
           format: int32
           description: User Status
-        arbitraryObject:
+        objectWithNoDeclaredProps:
           type: object
           description: test code generation for objects
             Value must be a map of strings to values. It cannot be the 'null' value.
-        arbitraryNullableObject:
+        objectWithNoDeclaredPropsNullable:
           type: object
           description: test code generation for nullable objects.
             Value must be a map of strings to values or the 'null' value.
           nullable: true
-        arbitraryTypeValue:
+        anyTypeProp:
           description: test code generation for any type
-            Value can be any type - string, number, boolean, array or object.
-        arbitraryNullableTypeValue:
+            Here the 'type' attribute is not specified, which means the value can be anything,
+            including the null value, string, number, boolean, array or object.
+            See https://github.com/OAI/OpenAPI-Specification/issues/1389
+        # TODO: this should be supported, currently there are some issues in the code generation.
+        #anyTypeExceptNullProp:
+        #  description: any type except 'null'
+        #    Here the 'type' attribute is not specified, which means the value can be anything,
+        #    including the null value, string, number, boolean, array or object.
+        #  not:
+        #    type: 'null'
+        anyTypePropNullable:
           description: test code generation for any type
-            Value can be any type - string, number, boolean, array, object or
-            the 'null' value.
+            Here the 'type' attribute is not specified, which means the value can be anything,
+            including the null value, string, number, boolean, array or object.
+            The 'nullable' attribute does not change the allowed values.
           nullable: true
       xml:
         name: User
@@ -1859,6 +1869,7 @@ components:
           - $ref: '#/components/schemas/banana'
     fruitReq:
        oneOf:
+          - type: 'null'
           - $ref: '#/components/schemas/appleReq'
           - $ref: '#/components/schemas/bananaReq'
     appleReq:
diff --git a/samples/client/petstore/python-experimental/petstore_api/model_utils.py b/samples/client/petstore/python-experimental/petstore_api/model_utils.py
index e4582083439f..b420b770d28f 100644
--- a/samples/client/petstore/python-experimental/petstore_api/model_utils.py
+++ b/samples/client/petstore/python-experimental/petstore_api/model_utils.py
@@ -1419,7 +1419,7 @@ def get_oneof_instance(self, model_args, constant_args):
             and path to item.
 
     Returns
-        oneof_instance (instance/None)
+        oneof_instance (instance)
     """
     if len(self._composed_schemas['oneOf']) == 0:
         return None
@@ -1428,6 +1428,13 @@ def get_oneof_instance(self, model_args, constant_args):
     # Iterate over each oneOf schema and determine if the input data
     # matches the oneOf schemas.
     for oneof_class in self._composed_schemas['oneOf']:
+        # The composed oneOf schema allows the 'null' type and the input data
+        # is the null value. This is a OAS >= 3.1 feature.
+        if oneof_class is none_type:
+            # skip none_types because we are deserializing dict data.
+            # none_type deserialization is handled in the __new__ method
+            continue
+
         # transform js keys from input data to python keys in fixed_model_args
         fixed_model_args = change_keys_js_to_python(
             model_args, oneof_class)
@@ -1473,9 +1480,11 @@ def get_anyof_instances(self, model_args, constant_args):
     Args:
         self: the class we are handling
         model_args (dict): var_name to var_value
-            used to make instances
+            The input data, e.g. the payload that must match at least one
+            anyOf child schema in the OpenAPI document.
         constant_args (dict): var_name to var_value
-            used to make instances
+            args that every model requires, including configuration, server
+            and path to item.
 
     Returns
         anyof_instances (list)
@@ -1485,6 +1494,13 @@ def get_anyof_instances(self, model_args, constant_args):
         return anyof_instances
 
     for anyof_class in self._composed_schemas['anyOf']:
+        # The composed oneOf schema allows the 'null' type and the input data
+        # is the null value. This is a OAS >= 3.1 feature.
+        if anyof_class is none_type:
+            # skip none_types because we are deserializing dict data.
+            # none_type deserialization is handled in the __new__ method
+            continue
+
         # transform js keys to python keys in fixed_model_args
         fixed_model_args = change_keys_js_to_python(model_args, anyof_class)
 
diff --git a/samples/openapi3/client/petstore/go-experimental/go-petstore/docs/User.md b/samples/openapi3/client/petstore/go-experimental/go-petstore/docs/User.md
index bd4a766983e0..26c9305363e8 100644
--- a/samples/openapi3/client/petstore/go-experimental/go-petstore/docs/User.md
+++ b/samples/openapi3/client/petstore/go-experimental/go-petstore/docs/User.md
@@ -321,6 +321,16 @@ SetArbitraryTypeValue sets ArbitraryTypeValue field to given value.
 
 HasArbitraryTypeValue returns a boolean if a field has been set.
 
+### SetArbitraryTypeValueNil
+
+`func (o *User) SetArbitraryTypeValueNil(b bool)`
+
+ SetArbitraryTypeValueNil sets the value for ArbitraryTypeValue to be an explicit nil
+
+### UnsetArbitraryTypeValue
+`func (o *User) UnsetArbitraryTypeValue()`
+
+UnsetArbitraryTypeValue ensures that no value is present for ArbitraryTypeValue, not even an explicit nil
 ### GetArbitraryNullableTypeValue
 
 `func (o *User) GetArbitraryNullableTypeValue() interface{}`
diff --git a/samples/openapi3/client/petstore/go-experimental/go-petstore/model_user.go b/samples/openapi3/client/petstore/go-experimental/go-petstore/model_user.go
index bee4da234d07..f9824d767f22 100644
--- a/samples/openapi3/client/petstore/go-experimental/go-petstore/model_user.go
+++ b/samples/openapi3/client/petstore/go-experimental/go-petstore/model_user.go
@@ -29,7 +29,7 @@ type User struct {
 	// test code generation for nullable objects. Value must be a map of strings to values or the 'null' value.
 	ArbitraryNullableObject map[string]interface{} `json:"arbitraryNullableObject,omitempty"`
 	// test code generation for any type Value can be any type - string, number, boolean, array or object.
-	ArbitraryTypeValue *interface{} `json:"arbitraryTypeValue,omitempty"`
+	ArbitraryTypeValue interface{} `json:"arbitraryTypeValue,omitempty"`
 	// test code generation for any type Value can be any type - string, number, boolean, array, object or the 'null' value.
 	ArbitraryNullableTypeValue interface{} `json:"arbitraryNullableTypeValue,omitempty"`
 }
@@ -372,22 +372,23 @@ func (o *User) SetArbitraryNullableObject(v map[string]interface{}) {
 	o.ArbitraryNullableObject = v
 }
 
-// GetArbitraryTypeValue returns the ArbitraryTypeValue field value if set, zero value otherwise.
+// GetArbitraryTypeValue returns the ArbitraryTypeValue field value if set, zero value otherwise (both if not set or set to explicit null).
 func (o *User) GetArbitraryTypeValue() interface{} {
-	if o == nil || o.ArbitraryTypeValue == nil {
+	if o == nil  {
 		var ret interface{}
 		return ret
 	}
-	return *o.ArbitraryTypeValue
+	return o.ArbitraryTypeValue
 }
 
 // GetArbitraryTypeValueOk returns a tuple with the ArbitraryTypeValue field value if set, nil otherwise
 // and a boolean to check if the value has been set.
+// NOTE: If the value is an explicit nil, `nil, true` will be returned
 func (o *User) GetArbitraryTypeValueOk() (*interface{}, bool) {
 	if o == nil || o.ArbitraryTypeValue == nil {
 		return nil, false
 	}
-	return o.ArbitraryTypeValue, true
+	return &o.ArbitraryTypeValue, true
 }
 
 // HasArbitraryTypeValue returns a boolean if a field has been set.
@@ -401,7 +402,7 @@ func (o *User) HasArbitraryTypeValue() bool {
 
 // SetArbitraryTypeValue gets a reference to the given interface{} and assigns it to the ArbitraryTypeValue field.
 func (o *User) SetArbitraryTypeValue(v interface{}) {
-	o.ArbitraryTypeValue = &v
+	o.ArbitraryTypeValue = v
 }
 
 // GetArbitraryNullableTypeValue returns the ArbitraryNullableTypeValue field value if set, zero value otherwise (both if not set or set to explicit null).
diff --git a/samples/openapi3/client/petstore/python-experimental/docs/User.md b/samples/openapi3/client/petstore/python-experimental/docs/User.md
index 8bf33039d830..2d9e43b532c2 100644
--- a/samples/openapi3/client/petstore/python-experimental/docs/User.md
+++ b/samples/openapi3/client/petstore/python-experimental/docs/User.md
@@ -11,10 +11,10 @@ Name | Type | Description | Notes
 **password** | **str** |  | [optional] 
 **phone** | **str** |  | [optional] 
 **user_status** | **int** | User Status | [optional] 
-**arbitrary_object** | **bool, date, datetime, dict, float, int, list, str** | test code generation for objects Value must be a map of strings to values. It cannot be the &#39;null&#39; value. | [optional] 
-**arbitrary_nullable_object** | **bool, date, datetime, dict, float, int, list, str, none_type** | test code generation for nullable objects. Value must be a map of strings to values or the &#39;null&#39; value. | [optional] 
-**arbitrary_type_value** | **bool, date, datetime, dict, float, int, list, str, none_type** | test code generation for any type Value can be any type - string, number, boolean, array or object. | [optional] 
-**arbitrary_nullable_type_value** | **bool, date, datetime, dict, float, int, list, str, none_type** | test code generation for any type Value can be any type - string, number, boolean, array, object or the &#39;null&#39; value. | [optional] 
+**object_with_no_declared_props** | **bool, date, datetime, dict, float, int, list, str** | test code generation for objects Value must be a map of strings to values. It cannot be the &#39;null&#39; value. | [optional] 
+**object_with_no_declared_props_nullable** | **bool, date, datetime, dict, float, int, list, str, none_type** | test code generation for nullable objects. Value must be a map of strings to values or the &#39;null&#39; value. | [optional] 
+**any_type_prop** | **bool, date, datetime, dict, float, int, list, str, none_type** | test code generation for any type Here the &#39;type&#39; attribute is not specified, which means the value can be anything, including the null value, string, number, boolean, array or object. See https://github.com/OAI/OpenAPI-Specification/issues/1389 | [optional] 
+**any_type_prop_nullable** | **bool, date, datetime, dict, float, int, list, str, none_type** | test code generation for any type Here the &#39;type&#39; attribute is not specified, which means the value can be anything, including the null value, string, number, boolean, array or object. The &#39;nullable&#39; attribute does not change the allowed values. | [optional] 
 
 [[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
 
diff --git a/samples/openapi3/client/petstore/python-experimental/petstore_api/model_utils.py b/samples/openapi3/client/petstore/python-experimental/petstore_api/model_utils.py
index e4582083439f..b420b770d28f 100644
--- a/samples/openapi3/client/petstore/python-experimental/petstore_api/model_utils.py
+++ b/samples/openapi3/client/petstore/python-experimental/petstore_api/model_utils.py
@@ -1419,7 +1419,7 @@ def get_oneof_instance(self, model_args, constant_args):
             and path to item.
 
     Returns
-        oneof_instance (instance/None)
+        oneof_instance (instance)
     """
     if len(self._composed_schemas['oneOf']) == 0:
         return None
@@ -1428,6 +1428,13 @@ def get_oneof_instance(self, model_args, constant_args):
     # Iterate over each oneOf schema and determine if the input data
     # matches the oneOf schemas.
     for oneof_class in self._composed_schemas['oneOf']:
+        # The composed oneOf schema allows the 'null' type and the input data
+        # is the null value. This is a OAS >= 3.1 feature.
+        if oneof_class is none_type:
+            # skip none_types because we are deserializing dict data.
+            # none_type deserialization is handled in the __new__ method
+            continue
+
         # transform js keys from input data to python keys in fixed_model_args
         fixed_model_args = change_keys_js_to_python(
             model_args, oneof_class)
@@ -1473,9 +1480,11 @@ def get_anyof_instances(self, model_args, constant_args):
     Args:
         self: the class we are handling
         model_args (dict): var_name to var_value
-            used to make instances
+            The input data, e.g. the payload that must match at least one
+            anyOf child schema in the OpenAPI document.
         constant_args (dict): var_name to var_value
-            used to make instances
+            args that every model requires, including configuration, server
+            and path to item.
 
     Returns
         anyof_instances (list)
@@ -1485,6 +1494,13 @@ def get_anyof_instances(self, model_args, constant_args):
         return anyof_instances
 
     for anyof_class in self._composed_schemas['anyOf']:
+        # The composed oneOf schema allows the 'null' type and the input data
+        # is the null value. This is a OAS >= 3.1 feature.
+        if anyof_class is none_type:
+            # skip none_types because we are deserializing dict data.
+            # none_type deserialization is handled in the __new__ method
+            continue
+
         # transform js keys to python keys in fixed_model_args
         fixed_model_args = change_keys_js_to_python(model_args, anyof_class)
 
diff --git a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/fruit_req.py b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/fruit_req.py
index a1836e551c0e..130f8781a7f3 100644
--- a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/fruit_req.py
+++ b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/fruit_req.py
@@ -218,5 +218,6 @@ def _composed_schemas():
           'oneOf': [
               apple_req.AppleReq,
               banana_req.BananaReq,
+              none_type,
           ],
         }
diff --git a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/user.py b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/user.py
index 2ed7428715bd..b8d64ff38c3a 100644
--- a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/user.py
+++ b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/user.py
@@ -85,10 +85,10 @@ def openapi_types():
             'password': (str,),  # noqa: E501
             'phone': (str,),  # noqa: E501
             'user_status': (int,),  # noqa: E501
-            'arbitrary_object': (bool, date, datetime, dict, float, int, list, str,),  # noqa: E501
-            'arbitrary_nullable_object': (bool, date, datetime, dict, float, int, list, str, none_type,),  # noqa: E501
-            'arbitrary_type_value': (bool, date, datetime, dict, float, int, list, str, none_type,),  # noqa: E501
-            'arbitrary_nullable_type_value': (bool, date, datetime, dict, float, int, list, str, none_type,),  # noqa: E501
+            'object_with_no_declared_props': (bool, date, datetime, dict, float, int, list, str,),  # noqa: E501
+            'object_with_no_declared_props_nullable': (bool, date, datetime, dict, float, int, list, str, none_type,),  # noqa: E501
+            'any_type_prop': (bool, date, datetime, dict, float, int, list, str, none_type,),  # noqa: E501
+            'any_type_prop_nullable': (bool, date, datetime, dict, float, int, list, str, none_type,),  # noqa: E501
         }
 
     @cached_property
@@ -104,10 +104,10 @@ def discriminator():
         'password': 'password',  # noqa: E501
         'phone': 'phone',  # noqa: E501
         'user_status': 'userStatus',  # noqa: E501
-        'arbitrary_object': 'arbitraryObject',  # noqa: E501
-        'arbitrary_nullable_object': 'arbitraryNullableObject',  # noqa: E501
-        'arbitrary_type_value': 'arbitraryTypeValue',  # noqa: E501
-        'arbitrary_nullable_type_value': 'arbitraryNullableTypeValue',  # noqa: E501
+        'object_with_no_declared_props': 'objectWithNoDeclaredProps',  # noqa: E501
+        'object_with_no_declared_props_nullable': 'objectWithNoDeclaredPropsNullable',  # noqa: E501
+        'any_type_prop': 'anyTypeProp',  # noqa: E501
+        'any_type_prop_nullable': 'anyTypePropNullable',  # noqa: E501
     }
 
     _composed_schemas = {}
@@ -162,10 +162,10 @@ def __init__(self, _check_type=True, _from_server=False, _path_to_item=(), _conf
             password (str): [optional]  # noqa: E501
             phone (str): [optional]  # noqa: E501
             user_status (int): User Status. [optional]  # noqa: E501
-            arbitrary_object (bool, date, datetime, dict, float, int, list, str): test code generation for objects Value must be a map of strings to values. It cannot be the &#39;null&#39; value.. [optional]  # noqa: E501
-            arbitrary_nullable_object (bool, date, datetime, dict, float, int, list, str, none_type): test code generation for nullable objects. Value must be a map of strings to values or the &#39;null&#39; value.. [optional]  # noqa: E501
-            arbitrary_type_value (bool, date, datetime, dict, float, int, list, str, none_type): test code generation for any type Value can be any type - string, number, boolean, array or object.. [optional]  # noqa: E501
-            arbitrary_nullable_type_value (bool, date, datetime, dict, float, int, list, str, none_type): test code generation for any type Value can be any type - string, number, boolean, array, object or the &#39;null&#39; value.. [optional]  # noqa: E501
+            object_with_no_declared_props (bool, date, datetime, dict, float, int, list, str): test code generation for objects Value must be a map of strings to values. It cannot be the &#39;null&#39; value.. [optional]  # noqa: E501
+            object_with_no_declared_props_nullable (bool, date, datetime, dict, float, int, list, str, none_type): test code generation for nullable objects. Value must be a map of strings to values or the &#39;null&#39; value.. [optional]  # noqa: E501
+            any_type_prop (bool, date, datetime, dict, float, int, list, str, none_type): test code generation for any type Here the &#39;type&#39; attribute is not specified, which means the value can be anything, including the null value, string, number, boolean, array or object. See https://github.com/OAI/OpenAPI-Specification/issues/1389. [optional]  # noqa: E501
+            any_type_prop_nullable (bool, date, datetime, dict, float, int, list, str, none_type): test code generation for any type Here the &#39;type&#39; attribute is not specified, which means the value can be anything, including the null value, string, number, boolean, array or object. The &#39;nullable&#39; attribute does not change the allowed values.. [optional]  # noqa: E501
         """
 
         self._data_store = {}
diff --git a/samples/openapi3/client/petstore/python-experimental/test/test_fruit_req.py b/samples/openapi3/client/petstore/python-experimental/test/test_fruit_req.py
index c1aa9f2255a2..21e55747e102 100644
--- a/samples/openapi3/client/petstore/python-experimental/test/test_fruit_req.py
+++ b/samples/openapi3/client/petstore/python-experimental/test/test_fruit_req.py
@@ -72,6 +72,7 @@ def testFruitReq(self):
                 'oneOf': [
                     petstore_api.AppleReq,
                     petstore_api.BananaReq,
+                    type(None),
                 ],
             }
         )
diff --git a/samples/openapi3/client/petstore/python-experimental/tests/test_deserialization.py b/samples/openapi3/client/petstore/python-experimental/tests/test_deserialization.py
index d40f3468428e..2d8e3de5e72a 100644
--- a/samples/openapi3/client/petstore/python-experimental/tests/test_deserialization.py
+++ b/samples/openapi3/client/petstore/python-experimental/tests/test_deserialization.py
@@ -161,3 +161,18 @@ def test_deserialize_mammal(self):
         self.assertTrue(isinstance(deserialized, petstore_api.Zebra))
         self.assertEqual(deserialized.type, zebra_type)
         self.assertEqual(deserialized.class_name, class_name)
+
+    def test_deserialize_fruit_null_value(self):
+        """
+        deserialize fruit with null value.
+        fruitReq is a oneOf composed schema model with discriminator, including 'null' type.
+        """
+
+        # Unmarshal 'null' value
+        data = None
+        response = MockResponse(data=json.dumps(data))
+        deserialized = self.deserialize(response, (petstore_api.FruitReq, type(None)), True)
+        self.assertEqual(type(deserialized), type(None))
+
+        inst = petstore_api.FruitReq(None)
+        self.assertIsNone(inst)