diff --git a/PIL/Image.py b/PIL/Image.py
index 839700a0f..851ef0b9c 100644
--- a/PIL/Image.py
+++ b/PIL/Image.py
@@ -1785,18 +1785,14 @@ class Image(object):
         :returns: None
         """
 
-        # preserve aspect ratio
-        x, y = self.size
-        if x > size[0]:
-            y = int(max(y * size[0] / x, 1))
-            x = int(size[0])
-        if y > size[1]:
-            x = int(max(x * size[1] / y, 1))
-            y = int(size[1])
-        size = x, y
-
         if size == self.size:
             return
+        # preserve aspect ratio
+        x, y = self.size
+        if x > size[0] or y > size[1]:
+            factor = max(x/size[0], y/size[1])
+            x, y = int(x/factor), int(y/factor)
+        size = x, y
 
         self.draft(None, size)