diff --git a/resize.py b/resize.py
index ffd10ca..93f6862 100755
--- a/resize.py
+++ b/resize.py
@@ -19,6 +19,7 @@ infile = args.source
 outfile = args.destination
 try:
     im = Image.open(infile)
+    format = im.format
     im = im.convert()
     if args.width is not None or args.height is not None:
         if args.width is None:
@@ -55,7 +56,7 @@ try:
     if args.enhance:
         enhancer = ImageEnhance.Contrast(im)
         im = enhancer.enhance(1.05)
-    im.save(outfile, "JPEG", quality=100)
+    im.save(outfile, format, quality=100)
 except IOError as e:
     print("cannot create thumbnail for '%s'" % infile)
     print "I/O error({0}): {1}".format(e.errno, e.strerror)