diff --git a/common/os/os.cxx b/common/os/os.cxx
index 52f4cb0e2a..6373b8d6f4 100644
--- a/common/os/os.cxx
+++ b/common/os/os.cxx
@@ -38,6 +38,7 @@
 #include <windows.h>
 #include <wininet.h> /* MinGW needs it */
 #include <shlobj.h>
+#define UNUSED(...) (void)(__VA_ARGS__)
 #endif
 
 static const char* getvncdir(bool userDir, const char *xdg_env, const char *xdg_def)
@@ -84,6 +85,7 @@ static const char* getvncdir(bool userDir, const char *xdg_env, const char *xdg_
 
   return dir;
 #else
+  UNUSED(xdg_def, xdg_env);
   if (userDir)
     ret = SHGetSpecialFolderPath(NULL, dir, CSIDL_PROFILE, FALSE);
   else