--- a/lisp/window.el
+++ b/lisp/window.el
@@ -1716,9 +1716,11 @@ window-sizable
   (setq window (window-normalize-window window))
   (cond
    ((< delta 0)
-    (max (- (window-min-size window horizontal ignore pixelwise)
-	    (window-size window horizontal pixelwise))
-	 delta))
+    (let ((min-size (window-min-size window horizontal ignore pixelwise))
+          (size (window-size window horizontal pixelwise)))
+      (if (<= size min-size)
+          0
+        (max (- min-size size) delta))))
    ((> delta 0)
     (if (window-size-fixed-p window horizontal ignore)
 	0