diff --git a/include/extern.h b/include/extern.h
index 15234fa8e..6a9ce1b30 100644
--- a/include/extern.h
+++ b/include/extern.h
@@ -1939,7 +1939,7 @@ E void FDECL(mselftouch, (struct monst *,const char *,BOOLEAN_P));
 E void NDECL(float_up);
 E void FDECL(fill_pit, (int,int));
 E int FDECL(float_down, (long, long));
-E int FDECL(fire_damage, (struct obj *,BOOLEAN_P,BOOLEAN_P,xchar,xchar));
+E int FDECL(fire_damage, (struct obj *,BOOLEAN_P,BOOLEAN_P,XCHAR_P,XCHAR_P));
 E void FDECL(water_damage, (struct obj *,BOOLEAN_P,BOOLEAN_P));
 E boolean NDECL(drown);
 E void FDECL(drain_en, (int));