diff --git a/openapi_schema_validator/_validators.py b/openapi_schema_validator/_validators.py
index b48f694..f0144ab 100644
--- a/openapi_schema_validator/_validators.py
+++ b/openapi_schema_validator/_validators.py
@@ -18,26 +18,6 @@
 from jsonschema.protocols import Validator
 
 
-def include_nullable_validator(
-    schema: Dict[Hashable, Any]
-) -> ItemsView[Hashable, Any]:
-    """
-    Include ``nullable`` validator always.
-    Suitable for use with `create`'s ``applicable_validators`` argument.
-    """
-    _schema = deepcopy(schema)
-
-    # append defaults to trigger nullable validator
-    if "nullable" not in _schema:
-        _schema.update(
-            {
-                "nullable": False,
-            }
-        )
-
-    return _schema.items()
-
-
 def handle_discriminator(
     validator: Validator, _: Any, instance: Any, schema: Mapping[Hashable, Any]
 ) -> Iterator[ValidationError]:
@@ -127,7 +107,14 @@ def type(
     schema: Mapping[Hashable, Any],
 ) -> Iterator[ValidationError]:
     if instance is None:
-        return
+        # nullable implementation based on OAS 3.0.3
+        # * nullable is only meaningful if its value is true
+        # * nullable: true is only meaningful in combination with a type
+        #   assertion specified in the same Schema Object.
+        # * nullable: true operates within a single Schema Object
+        if "nullable" in schema and schema["nullable"] == True:
+            return
+        yield ValidationError("None for not nullable")
 
     if not validator.is_type(instance, data_type):
         data_repr = repr(data_type)
@@ -163,16 +150,6 @@ def items(
         yield from validator.descend(item, items, path=index)
 
 
-def nullable(
-    validator: Validator,
-    is_nullable: bool,
-    instance: Any,
-    schema: Mapping[Hashable, Any],
-) -> Iterator[ValidationError]:
-    if instance is None and not is_nullable:
-        yield ValidationError("None for not nullable")
-
-
 def required(
     validator: Validator,
     required: List[str],
diff --git a/openapi_schema_validator/validators.py b/openapi_schema_validator/validators.py
index c8d68b4..f4b12ea 100644
--- a/openapi_schema_validator/validators.py
+++ b/openapi_schema_validator/validators.py
@@ -45,7 +45,6 @@
         # TODO: adjust default
         "$ref": _validators.ref,
         # fixed OAS fields
-        "nullable": oas_validators.nullable,
         "discriminator": oas_validators.not_implemented,
         "readOnly": oas_validators.readOnly,
         "writeOnly": oas_validators.writeOnly,
@@ -59,7 +58,6 @@
     # See https://github.com/p1c2u/openapi-schema-validator/pull/12
     # version="oas30",
     id_of=lambda schema: schema.get("id", ""),
-    applicable_validators=oas_validators.include_nullable_validator,
 )
 
 OAS31Validator = extend(
diff --git a/tests/integration/test_validators.py b/tests/integration/test_validators.py
index 47ea5da..1bbc9f6 100644
--- a/tests/integration/test_validators.py
+++ b/tests/integration/test_validators.py
@@ -31,6 +31,16 @@ def test_null(self, schema_type):
         with pytest.raises(ValidationError):
             validator.validate(value)
 
+    @pytest.mark.parametrize("is_nullable", [True, False])
+    def test_nullable_untyped(self, is_nullable):
+        schema = {"nullable": is_nullable}
+        validator = OAS30Validator(schema)
+        value = None
+
+        result = validator.validate(value)
+
+        assert result is None
+
     @pytest.mark.parametrize(
         "schema_type",
         [
@@ -50,6 +60,23 @@ def test_nullable(self, schema_type):
 
         assert result is None
 
+    def test_nullable_enum_without_none(self):
+        schema = {"type": "integer", "nullable": True, "enum": [1, 2, 3]}
+        validator = OAS30Validator(schema)
+        value = None
+
+        with pytest.raises(ValidationError):
+            validator.validate(value)
+
+    def test_nullable_enum_with_none(self):
+        schema = {"type": "integer", "nullable": True, "enum": [1, 2, 3, None]}
+        validator = OAS30Validator(schema)
+        value = None
+
+        result = validator.validate(value)
+
+        assert result is None
+
     @pytest.mark.parametrize(
         "value",
         [
@@ -442,6 +469,103 @@ def test_oneof_discriminator(self, schema_type):
             result = validator.validate({"discipline": "other"})
             assert False
 
+    @pytest.mark.parametrize("is_nullable", [True, False])
+    def test_nullable_ref(self, is_nullable):
+        """
+        Tests that a field that points to a schema reference is null checked based on the $ref schema rather than
+        on this schema
+        :param is_nullable:  if the schema is marked as nullable. If not, validate an exception is raised on None
+        """
+        schema = {
+            "$ref": "#/$defs/Pet",
+            "$defs": {
+                "NullableText": {
+                    "type": "string",
+                    "nullable": is_nullable
+                },
+                "Pet": {
+                    "properties": {
+                        "testfield": {"$ref": "#/$defs/NullableText"},
+                    },
+                }
+            },
+        }
+        validator = OAS30Validator(
+            schema,
+            format_checker=oas30_format_checker,
+        )
+
+        result = validator.validate({"testfield": "John"})
+        assert result is None
+
+        if is_nullable:
+            result = validator.validate({"testfield": None})
+            assert result is None
+        else:
+            with pytest.raises(
+                    ValidationError,
+                    match="None for not nullable",
+            ):
+                validator.validate({"testfield": None})
+                assert False
+
+
+    @pytest.mark.parametrize(
+        "schema_type, not_nullable_regex",
+        [
+            ("oneOf", "None is not valid under any of the given schemas"),
+            ("anyOf", "None is not valid under any of the given schemas"),
+            ("allOf", "None for not nullable")
+        ],
+    )
+    @pytest.mark.parametrize("is_nullable", [True, False])
+    def test_nullable_schema_combos(self, is_nullable, schema_type, not_nullable_regex):
+        """
+        This test ensures that nullablilty semantics are correct for oneOf, anyOf and allOf
+        Specifically, nullable should checked on the children schemas
+        :param is_nullable:  if the schema is marked as nullable. If not, validate an exception is raised on None
+        :param schema_type: the schema type to validate
+        :param not_nullable_regex: the expected raised exception if fields are marked as not nullable
+        """
+        schema = {
+            "$ref": "#/$defs/Pet",
+            "$defs": {
+                "NullableText": {
+                    "type": "string",
+                    "nullable": False if schema_type == "oneOf" else is_nullable
+                },
+                "NullableEnum": {
+                    "type": "string",
+                    "nullable": is_nullable,
+                    "enum": ["John", "Alice", None]
+                },
+                "Pet": {
+                    "properties": {
+                        "testfield": {
+                            schema_type: [
+                                {"$ref": "#/$defs/NullableText"},
+                                {"$ref": "#/$defs/NullableEnum"},
+                            ]
+                        }
+                    },
+                }
+            },
+        }
+        validator = OAS30Validator(
+            schema,
+            format_checker=oas30_format_checker,
+        )
+
+        if is_nullable:
+            result = validator.validate({"testfield": None})
+            assert result is None
+        else:
+            with pytest.raises(
+                    ValidationError,
+                    match=not_nullable_regex
+            ):
+                validator.validate({"testfield": None})
+                assert False
 
 class TestOAS31ValidatorValidate:
     @pytest.mark.parametrize(