diff --git a/win/rfb_win32/CleanDesktop.cxx b/win/rfb_win32/CleanDesktop.cxx
index bad95f0..90b3451 100644
--- a/win/rfb_win32/CleanDesktop.cxx
+++ b/win/rfb_win32/CleanDesktop.cxx
@@ -148,7 +148,7 @@
   DWORD r = ERROR_SUCCESS;
   if (!SystemParametersInfo(action, param, ptr, ini)) {
     r = GetLastError();
-    vlog.info("SPI error: %d", r);
+    vlog.info("SPI error: %lu", r);
   }
   return r;
 }