From 753be1a8bdb79c0b79b113ea3e79ddccd63f3d1a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cristi=20V=C3=AEjdea?= <cristi@cvjd.me>
Date: Thu, 13 Jun 2019 13:43:13 +0300
Subject: [PATCH] Fix potential issubclass crash

---
 src/drf_yasg/inspectors/field.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/drf_yasg/inspectors/field.py b/src/drf_yasg/inspectors/field.py
index 9f063b6..6527db4 100644
--- a/src/drf_yasg/inspectors/field.py
+++ b/src/drf_yasg/inspectors/field.py
@@ -610,7 +610,7 @@ class SerializerMethodFieldInspector(FieldInspector):
             # look for Python 3.5+ style type hinting of the return value
             hint_class = inspect_signature(method).return_annotation
 
-            if not issubclass(hint_class, inspect._empty):
+            if inspect.isclass(hint_class) and not issubclass(hint_class, inspect._empty):
                 type_info = get_basic_type_info_from_hint(hint_class)
 
                 if type_info is not None: