diff --git a/common/rfb/Decoder.cxx b/common/rfb/Decoder.cxx
index b6e4fd5..61d8bce 100644
--- a/common/rfb/Decoder.cxx
+++ b/common/rfb/Decoder.cxx
@@ -32,19 +32,19 @@
 
 DecoderCreateFnType Decoder::createFns[encodingMax+1] = { 0 };
 
-bool Decoder::supported(unsigned int encoding)
+bool Decoder::supported(int encoding)
 {
   return encoding <= encodingMax && createFns[encoding];
 }
 
-Decoder* Decoder::createDecoder(unsigned int encoding, CMsgReader* reader)
+Decoder* Decoder::createDecoder(int encoding, CMsgReader* reader)
 {
   if (encoding <= encodingMax && createFns[encoding])
     return (*createFns[encoding])(reader);
   return 0;
 }
 
-void Decoder::registerDecoder(unsigned int encoding,
+void Decoder::registerDecoder(int encoding,
                               DecoderCreateFnType createFn)
 {
   if (encoding > encodingMax)