diff --git a/zipline/testing/predicates.py b/zipline/testing/predicates.py
index fa776ba1..e6d34e5f 100644
--- a/zipline/testing/predicates.py
+++ b/zipline/testing/predicates.py
@@ -358,7 +358,7 @@ def assert_dict_equal(result, expected, path=(), msg='', **kwargs):
             assert_equal(
                 resultv,
                 expectedv,
-                path=path + ('[%r]' % k,),
+                path=path + ('[%r]' % (k,),),
                 msg=msg,
                 **kwargs
             )