diff --git a/gtk/gtkwin32.c b/gtk/gtkwin32.c
index 2144279e03..71cb2c0597 100644
--- a/gtk/gtkwin32.c
+++ b/gtk/gtkwin32.c
@@ -36,7 +36,7 @@
 extern IMAGE_DOS_HEADER __ImageBase;
 
 static inline HMODULE
-this_module ()
+this_module (void)
 {
   return (HMODULE) &__ImageBase;
 }