diff --git a/common/rfb/VNCSConnectionST.h b/common/rfb/VNCSConnectionST.h
index bc6ae5b..72ffc1d 100644
--- a/common/rfb/VNCSConnectionST.h
+++ b/common/rfb/VNCSConnectionST.h
@@ -186,7 +186,7 @@
 
     unsigned baseRTT;
     unsigned congWindow;
-    int ackedOffset, sentOffset;
+    unsigned ackedOffset, sentOffset;
 
     unsigned minRTT;
     bool seenCongestion;