diff --git a/hiyapyco/__init__.py b/hiyapyco/__init__.py
index 6e9e640..ac07a28 100644
--- a/hiyapyco/__init__.py
+++ b/hiyapyco/__init__.py
@@ -403,6 +403,7 @@ def _substmerge(self, a, b):
                 return None
             # default behavior is to attempt merge or fail
             logger.debug('pass as b is None')
+            pass
 
         # treat listTypes as primitiveTypes in merge
         # subsititues list, don't merge them