--- slige/slige.c.old
+++ slige/slige.c
@@ -9736,6 +9736,8 @@
   int i,count;
   float hl, am;
   int thisbit;
+  int allow_skull = 1;
+  char *cp;
 
   {
   char s[200];
@@ -9744,6 +9746,24 @@
   announce(NONE,s);
   }
 
+//--------------------------------------------------------------------
+
+// The following code makes it  possible for wrapper programs to block
+// the ID_SKULL  character.  This feature was added so that the spider
+// robots added by "haloween.wad" can be blocked  when that WAD is us-
+// ed.  [The  robots  in question are  "haloween.wad's" version of ID_
+// SKULL.  IMHO:  They don't seem to  fit with the rest of the charac-
+// ters.]
+
+    if ((cp = getenv ("PRFREESKULL")) != NULL)
+    {
+        int c = *cp;
+        if ((c >= 'a') && (c <= 'z')) c += 'A'-'a';
+        if ((c == 'F') || (c == 'N') || (c == '0')) allow_skull = 0;
+    }
+
+//--------------------------------------------------------------------
+
   require |= MONSTER;                         /* Duh! */
   forbid |= BOSS;                             /* No wandering bosses */
   if (!c->big_monsters) forbid |= BIG;
@@ -9758,6 +9778,8 @@
   for (m=c->genus_anchor;m;m=m->next) {
     if ((m->bits & require) != require) continue;
     if ((m->bits & forbid) != 0) continue;
+    if ((m->thingid == ID_SKULL) && !allow_skull) continue;
+
 #ifdef IMPOSSIBLE_MONSTERS_IN_CONFIG
     if ((m->gamemask&c->gamemask)!=c->gamemask) continue;
 #endif