diff --git a/Source/g_game.c b/Source/g_game.c
index 2c61ba29..7b93ca0d 100644
--- a/Source/g_game.c
+++ b/Source/g_game.c
@@ -2375,6 +2375,10 @@ byte *G_ReadOptions(byte *demo_p)
       for (i=0; i < COMP_TOTAL; i++)
 	comp[i] = compatibility;
 
+      // [FG] In Boom, monsters did not stay on a lift
+      comp[comp_staylift] = 1;
+      // [FG] Boom did not prevent zombies from exiting levels
+      comp[comp_zombie] = 1;
       // [FG] Boom never had the 3-key door bug
       comp[comp_3keydoor] = 1;
 
diff --git a/Source/p_floor.c b/Source/p_floor.c
index 0fd9df51..c12a9546 100644
--- a/Source/p_floor.c
+++ b/Source/p_floor.c
@@ -816,12 +816,20 @@ int EV_BuildStairs
         if (tsec->floorpic != texture)
           continue;
 
+	if (demo_compatibility || demo_version >= 203)
+	{
 	height += stairsize;  // killough 10/98: intentionally left this way
+	}
 
         // if sector's floor already moving, look for another
         if (P_SectorActive(floor_special,tsec)) //jff 2/22/98
 	  continue;
 
+	if (!demo_compatibility && demo_version < 203)
+	{
+	height += stairsize;
+	}
+
         sec = tsec;
         secnum = newsecnum;
 
@@ -849,7 +857,7 @@ int EV_BuildStairs
 
     // [FG] Compatibility bug in EV_BuildStairs
     // http://prboom.sourceforge.net/mbf-bugs.html
-    if (!comp[comp_stairs] && !demo_compatibility)      // killough 10/98: compatibility option
+    if ((!comp[comp_stairs] || demo_version < 203) && !demo_compatibility)      // killough 10/98: compatibility option
       secnum = osecnum;          //jff 3/4/98 restore loop index
   }
   return rtn;
diff --git a/Source/p_sight.c b/Source/p_sight.c
index ad78e455..8a99ffd4 100644
--- a/Source/p_sight.c
+++ b/Source/p_sight.c
@@ -250,7 +250,7 @@ boolean P_CheckSight(mobj_t *t1, mobj_t *t2)
   // killough 11/98: shortcut for melee situations
   // [FG] Compatibility bug in P_CheckSight
   // http://prboom.sourceforge.net/mbf-bugs.html
-  if (t1->subsector == t2->subsector && !demo_compatibility)     // same subsector? obviously visible
+  if (t1->subsector == t2->subsector && demo_version >= 203)     // same subsector? obviously visible
     return true;
 
   // An unobstructed LOS is possible.