diff --git a/common/rfb/EncodeManager.cxx b/common/rfb/EncodeManager.cxx
index 3142ec0..e632387 100644
--- a/common/rfb/EncodeManager.cxx
+++ b/common/rfb/EncodeManager.cxx
@@ -624,7 +624,7 @@
 
   // Special exception inherited from the Tight encoder
   if (activeEncoders[encoderFullColour] == encoderTightJPEG) {
-    if (conn->cp.compressLevel < 2)
+    if ((conn->cp.compressLevel != -1) && (conn->cp.compressLevel < 2))
       maxColours = 24;
     else
       maxColours = 96;