diff --git a/src/gui_w48.c b/src/gui_w48.c
index 164a9f9..345d4da 100644
--- a/src/gui_w48.c
+++ b/src/gui_w48.c
@@ -129,6 +129,7 @@
 typedef void VOID;
 typedef int LPNMHDR;
 typedef int LONG;
+typedef int WNDPROC;
 #endif
 
 #ifndef GET_X_LPARAM