diff --git a/src/statebag/__init__.py b/src/statebag/__init__.py
--- a/src/statebag/__init__.py
+++ b/src/statebag/__init__.py
@@ -60,7 +60,7 @@ class StateBag:
 	def pushState(self,board):
 		sn=BoardState(board)
 		if len(self._states)>0:
-			if sn==self._states[-1]: return None # no change
+			if sn==self._states[-1]: return self._states[-1] # no change
 			sn.cachedDiff=sn-self._states[-1]
 		else: sn.setWeight(1)