diff --git a/src/cryptography/x509/extensions.py b/src/cryptography/x509/extensions.py
index 74e271e..938a98e 100644
--- a/src/cryptography/x509/extensions.py
+++ b/src/cryptography/x509/extensions.py
@@ -82,7 +82,7 @@
 
     def get_extension_for_class(self, extclass):
         for ext in self:
-            if type(ext.value) == extclass:
+            if isinstance(ext.value, extclass):
                 return ext
 
         raise ExtensionNotFound("No {0} extension was found".format(extclass), extclass)