diff --git a/graphene/relay/mutation.py b/graphene/relay/mutation.py
index ee758e78..d9fa5c22 100644
--- a/graphene/relay/mutation.py
+++ b/graphene/relay/mutation.py
@@ -20,9 +20,9 @@ class ClientIDMutation(Mutation):
         assert not output, "Can't specify any output"
         assert not arguments, "Can't specify any arguments"
 
-        bases = (InputObjectType,)
+        bases = (InputObjectType, )
         if input_class:
-            bases += (input_class,)
+            bases = (input_class, ) + bases
 
         if not input_fields:
             input_fields = {}