diff --git a/DwmPromote.hs b/DwmPromote.hs
index 7792fdd9..68487cec 100644
--- a/DwmPromote.hs
+++ b/DwmPromote.hs
@@ -37,8 +37,8 @@ promote :: (Integral i, Ord a) => StackSet i j a -> StackSet i j a
 promote w = maybe w id $ do
     a <- peek w -- fail if null
     let stack = index (current w) w
-    let newstack = swap a (next stack a) stack
-    return $ w { stacks = M.insert (current w) newstack (stacks w),
+        newstack = swap a (next stack a) stack
+    return $ w { stacks = M.adjust (\(f,_) -> (f, newstack)) (current w) (stacks w),
                  focus = M.insert (current w) (head newstack) (focus w) }
   where
     next s a | head s /= a = head s -- focused is not master