diff --git a/drf_spectacular/openapi.py b/drf_spectacular/openapi.py
index d6a25f39..11c69f86 100644
--- a/drf_spectacular/openapi.py
+++ b/drf_spectacular/openapi.py
@@ -17,8 +17,8 @@
 from rest_framework.schemas.utils import get_pk_description, is_list_view
 
 from drf_spectacular.app_settings import spectacular_settings
-from drf_spectacular.plumbing import resolve_basic_type, warn, anyisinstance, force_instance, is_serializer, follow_field_source, is_field
-from drf_spectacular.types import OpenApiTypes, PYTHON_TYPE_MAPPING, OPENAPI_TYPE_MAPPING
+from drf_spectacular.plumbing import resolve_basic_type, warn, anyisinstance, force_instance, is_serializer, follow_field_source, is_field, is_basic_type
+from drf_spectacular.types import OpenApiTypes
 from drf_spectacular.utils import PolymorphicProxySerializer
 
 AUTHENTICATION_SCHEMES = {
@@ -378,7 +378,7 @@ def _map_model_field(self, field):
 
     def _map_serializer_field(self, method, field):
         if hasattr(field, '_spectacular_annotation'):
-            if field._spectacular_annotation in OPENAPI_TYPE_MAPPING or field._spectacular_annotation in PYTHON_TYPE_MAPPING:
+            if is_basic_type(field._spectacular_annotation):
                 return resolve_basic_type(field._spectacular_annotation)
             else:
                 return self._map_serializer_field(method, field._spectacular_annotation)
@@ -640,7 +640,7 @@ def _map_type_hint(self, method):
 
         if is_serializer(hint) or is_field(hint):
             return self._map_serializer_field(method, force_instance(hint))
-        elif hint in PYTHON_TYPE_MAPPING or hint in OPENAPI_TYPE_MAPPING:
+        elif is_basic_type(hint):
             return resolve_basic_type(hint)
         else:
             warn(f'type hint for function "{method.__name__}" is unknown. defaulting to string.')
diff --git a/drf_spectacular/plumbing.py b/drf_spectacular/plumbing.py
index 250ab878..d8ae4d8c 100644
--- a/drf_spectacular/plumbing.py
+++ b/drf_spectacular/plumbing.py
@@ -1,3 +1,4 @@
+import collections
 import inspect
 import sys
 
@@ -38,18 +39,24 @@ def is_field(obj):
     return isinstance(force_instance(obj), fields.Field) and not is_serializer(obj)
 
 
-def resolve_basic_type(type_):
+def is_basic_type(obj):
+    if not isinstance(obj, collections.Hashable):
+        return False
+    return obj in OPENAPI_TYPE_MAPPING or obj in PYTHON_TYPE_MAPPING
+
+
+def resolve_basic_type(obj):
     """
     resolve either enum or actual type and yield schema template for modification
     """
-    if type_ in OPENAPI_TYPE_MAPPING:
-        return dict(OPENAPI_TYPE_MAPPING[type_])
-    elif type_ in PYTHON_TYPE_MAPPING:
-        return dict(OPENAPI_TYPE_MAPPING[PYTHON_TYPE_MAPPING[type_]])
-    elif type_ is None or type(type_) is None:
+    if obj in OPENAPI_TYPE_MAPPING:
+        return dict(OPENAPI_TYPE_MAPPING[obj])
+    elif obj in PYTHON_TYPE_MAPPING:
+        return dict(OPENAPI_TYPE_MAPPING[PYTHON_TYPE_MAPPING[obj]])
+    elif obj is None or type(obj) is None:
         return dict(OPENAPI_TYPE_MAPPING[OpenApiTypes.NONE])
     else:
-        warn(f'could not resolve type "{type_}". defaulting to "string"')
+        warn(f'could not resolve type "{obj}". defaulting to "string"')
         return dict(OPENAPI_TYPE_MAPPING[OpenApiTypes.STR])