diff --git a/src/xpra/client/gtk2/window_backing.py b/src/xpra/client/gtk2/window_backing.py
index 46280f285e..9db86883ae 100644
--- a/src/xpra/client/gtk2/window_backing.py
+++ b/src/xpra/client/gtk2/window_backing.py
@@ -65,6 +65,8 @@ def paint_image(self, coding, img_data, x, y, width, height, options, callbacks)
 
     def paint_pixbuf_gdk(self, coding, img_data, x, y, width, height, options, callbacks):
         """ must be called from UI thread """
+        if coding.startswith("png"):
+            coding = "png"
         loader = gdk.PixbufLoader(coding)
         loader.write(img_data, len(img_data))
         loader.close()