diff --git a/src/xpra/codecs/pillow/encode.py b/src/xpra/codecs/pillow/encode.py
index 0ae311fcd9..8c6dd3118a 100644
--- a/src/xpra/codecs/pillow/encode.py
+++ b/src/xpra/codecs/pillow/encode.py
@@ -57,7 +57,7 @@ def encode(coding, image, quality, speed, supports_transparency):
         "RLE8"  : "P",
         "XRGB"  : "RGB",
         "BGRX"  : "RGB",
-        "RGBX"  : "RGBX",
+        "RGBX"  : "RGB",
         "RGBA"  : "RGBA",
         "BGRA"  : "RGBA",
         }.get(pixel_format, pixel_format)