diff --git a/PIL/GifImagePlugin.py b/PIL/GifImagePlugin.py
index 443d4db12..203689320 100644
--- a/PIL/GifImagePlugin.py
+++ b/PIL/GifImagePlugin.py
@@ -364,6 +364,11 @@ def getheader(im, palette=None, info=None):
         for i in range(maxcolor):
             s.append(o8(i) * 3)
 
+    if im.info.has_key('transparency'):
+        transparentIndex = im.info['transparency']
+        s.append('!' + o8(0xf9) + o8(4) + o8(1) + o8(0) + o8(0) +
+                 o8(transparentIndex) + o8(0))
+
     return s
 
 def getdata(im, offset = (0, 0), **params):
diff --git a/libImaging/Imaging.h b/libImaging/Imaging.h
index e2033022a..76861a0df 100644
--- a/libImaging/Imaging.h
+++ b/libImaging/Imaging.h
@@ -75,7 +75,7 @@ typedef struct ImagingPaletteInstance* ImagingPalette;
 struct ImagingMemoryInstance {
 
     /* Format */
-    char mode[4+1];	/* Band names ("1", "L", "P", "RGB", "RGBA", "CMYK") */
+    char mode[6+1];	/* Band names ("1", "L", "P", "RGB", "RGBA", "CMYK", "YCbCr", "BGR;xy") */
     int type;		/* Data type (IMAGING_TYPE_*) */
     int depth;		/* Depth (ignored in this version) */
     int bands;		/* Number of bands (1, 2, 3, or 4) */