diff --git a/common/rfb/PixelFormat.cxx b/common/rfb/PixelFormat.cxx

index a9d015d..896f4e5 100644

--- a/common/rfb/PixelFormat.cxx

+++ b/common/rfb/PixelFormat.cxx

@@ -200,6 +200,12 @@ bool PixelFormat::is888(void) const

     return false;

   if (blueMax != 255)

     return false;

+  if ((redShift & 0x7) != 0)

+    return false;

+  if ((greenShift & 0x7) != 0)

+    return false;

+  if ((blueShift & 0x7) != 0)

+    return false;

   return true;

 }