diff --git a/src/external/mud/src/mud.h b/src/external/mud/src/mud.h
index 2c9915f5..13bfb42d 100644
--- a/src/external/mud/src/mud.h
+++ b/src/external/mud/src/mud.h
@@ -213,7 +213,7 @@ typedef enum {
     MUD_HEADS = 5
 } MUD_OPT;
 
-typedef int (*MUD_PROC)(MUD_OPT, ...);
+typedef int (*MUD_PROC)(MUD_OPT, void *p1, void *p2);
 
 typedef enum {
     MUD_ONE = 1,