diff --git a/src/gui_w48.c b/src/gui_w48.c
index 07174cc..78aba03 100644
--- a/src/gui_w48.c
+++ b/src/gui_w48.c
@@ -3102,7 +3102,7 @@
  * 'guifont'
  */
     static void
-update_im_font()
+update_im_font(void)
 {
     LOGFONT	lf_wide;