diff --git a/libvncclient/ultra.c b/libvncclient/ultra.c
index dddb0c0..dac89b5 100644
--- a/libvncclient/ultra.c
+++ b/libvncclient/ultra.c
@@ -57,7 +57,7 @@ HandleUltraBPP (rfbClient* client, int rx, int ry, int rw, int rh)
    * buffer, this buffer allocation should only happen once, on the
    * first update.
    */
-  if ( client->raw_buffer_size < uncompressedBytes) {
+  if ( client->raw_buffer_size < (int)uncompressedBytes) {
     if ( client->raw_buffer != NULL ) {
       free( client->raw_buffer );
     }
@@ -141,7 +141,7 @@ HandleUltraZipBPP (rfbClient* client, int rx, int ry, int rw, int rh)
    * buffer, this buffer allocation should only happen once, on the
    * first update.
    */
-  if ( client->raw_buffer_size < (uncompressedBytes + 500)) {
+  if ( client->raw_buffer_size < (int)(uncompressedBytes + 500)) {
     if ( client->raw_buffer != NULL ) {
       free( client->raw_buffer );
     }
diff --git a/libvncserver/ultra.c b/libvncserver/ultra.c
index 47fab55..9485591 100644
--- a/libvncserver/ultra.c
+++ b/libvncserver/ultra.c
@@ -68,7 +68,7 @@ rfbSendOneRectEncodingUltra(rfbClientPtr cl,
      */
     maxCompSize = (maxRawSize + maxRawSize / 16 + 64 + 3);
 
-    if (cl->afterEncBufSize < maxCompSize) {
+    if (cl->afterEncBufSize < (int)maxCompSize) {
 	cl->afterEncBufSize = maxCompSize;
 	if (cl->afterEncBuf == NULL)
 	    cl->afterEncBuf = (char *)malloc(cl->afterEncBufSize);