diff --git a/graphene/types/mutation.py b/graphene/types/mutation.py
index 25794d47..ecdcb457 100644
--- a/graphene/types/mutation.py
+++ b/graphene/types/mutation.py
@@ -54,7 +54,10 @@ class Mutation(ObjectType):
                     ).format(name=cls.__name__))
 
             if input_class:
-                arguments = props(input_class)
+                if isinstance(input_class, dict):
+                    arguments = input_class
+                else:
+                    arguments = props(input_class)
             else:
                 arguments = {}