diff --git a/Satchmo/Counting/Direct.hs b/Satchmo/Counting/Direct.hs
--- a/Satchmo/Counting/Direct.hs
+++ b/Satchmo/Counting/Direct.hs
@@ -34,9 +34,11 @@
   that <- atmost k xs
   this B.&& that
 
-assert_implies_atmost ys k xs = 
+assert_implies_atmost ys k xs | k >= 0 = 
   forM_ (select (k+1) xs) $ \ sub -> do
     B.assert $ map B.not ys ++ map B.not sub
+assert_implies_atmost ys k _ =
+  B.assert $ map B.not ys
 
 -- | asserting that  (or ys)  implies  (exactly k xs)
 assert_implies_exactly ys k xs = do
diff --git a/satchmo.cabal b/satchmo.cabal
--- a/satchmo.cabal
+++ b/satchmo.cabal
@@ -1,5 +1,5 @@
 Name:           satchmo
-Version:        2.9.5
+Version:        2.9.6
 
 License:        GPL
 License-file:	gpl-2.0.txt