diff --git a/src/Data/SumBag.hs b/src/Data/SumBag.hs
index eaca38ad32153e20b686ca7fbfcd834aae3c5638..50226b8fa39a0ac792413b1fa787d672588d9828 100644
--- a/src/Data/SumBag.hs
+++ b/src/Data/SumBag.hs
@@ -135,7 +135,7 @@ balance1 a left right
     let Node _ _ lleft lright = left
         sizeLL = size lleft
         sizeLR = size lright
-    in if sizeLL < sizeLR then rotateSingleRight a left right else rotateDoubleRight a left right
+    in if sizeLR < sizeLL then rotateSingleRight a left right else rotateDoubleRight a left right
   -- No subtree is too heavy, we can just form a new tree straight away
   | otherwise = node a left right