diff --git a/media/asset.py b/media/asset.py
index fbd9b23..c8b4ad0 100644
--- a/media/asset.py
+++ b/media/asset.py
@@ -133,7 +133,7 @@ class MediaAssetFile(object):
                         mediaFile.crop(*dims)
                 elif command == "size":
                     size = [int(i) for i in args.split(",")]
-                    if size and len(size) == 2:
+                    if size:
                         mediaFile.resize(*size)
             outputFormat = self.getContentType(variant)
             mediaFile.save(path, outputFormat)
diff --git a/media/piltransform.py b/media/piltransform.py
index 56cfdc7..a040103 100644
--- a/media/piltransform.py
+++ b/media/piltransform.py
@@ -93,9 +93,13 @@ class PILTransform(object):
         box = (left, upper, right, lower)
         self.im = self.im.crop(box)
 
-    def resize(self, width, height):
+    def resize(self, width, height=None):
         if self.im is None:
             return
+        if not height:
+            ow, oh = self.im.size
+            ratio = float(ow) / float(oh)
+            height = int(round(float(width) / ratio))
         dims = (width, height)
         self.im.thumbnail(dims, Image.ANTIALIAS)