diff --git a/doc/fixes34.4 b/doc/fixes34.4
index 69031f814..533169d52 100644
--- a/doc/fixes34.4
+++ b/doc/fixes34.4
@@ -171,6 +171,8 @@ prevent "object lost" panic caused by accessing freed memory after worn
 	non-fireproof water walking boots are destroyed by lava
 stop multi-turn running, searching, or resting early if levitation ends
 Call command could be used to remotely identify which high priest is which
+large amorphous, whirly, noncorporeal, or slithy creatures can fit through
+	tight diagonal gaps despite their size
 
 
 Platform- and/or Interface-Specific Fixes
diff --git a/include/extern.h b/include/extern.h
index 0ba835021..2ec40316e 100644
--- a/include/extern.h
+++ b/include/extern.h
@@ -724,6 +724,7 @@ E void FDECL(movobj, (struct obj *,XCHAR_P,XCHAR_P));
 E boolean FDECL(may_dig, (XCHAR_P,XCHAR_P));
 E boolean FDECL(may_passwall, (XCHAR_P,XCHAR_P));
 E boolean FDECL(bad_rock, (struct permonst *,XCHAR_P,XCHAR_P));
+E int FDECL(cant_squeeze_thru, (struct monst *));
 E boolean FDECL(invocation_pos, (XCHAR_P,XCHAR_P));
 E boolean FDECL(test_move, (int, int, int, int, int));
 E void NDECL(domove);
diff --git a/src/hack.c b/src/hack.c
index 1486590c1..33a66cf35 100644
--- a/src/hack.c
+++ b/src/hack.c
@@ -526,6 +526,33 @@ register xchar x,y;
 		    && !(passes_walls(mdat) && may_passwall(x,y)))));
 }
 
+/* caller has already decided that it's a tight diagonal; check whether a
+   monster--who might be the hero--can fit through, and if not then return
+   the reason why:  1: can't fit, 2: possessions won't fit, 3: sokoban */
+int     /* returns 0 if we can squeeze through */
+cant_squeeze_thru(mon)
+struct monst *mon;
+{
+    int amt;
+    struct permonst *ptr = mon->data;
+
+    /* too big? */
+    if (bigmonst(ptr) &&
+	    !(amorphous(ptr) || is_whirly(ptr) ||
+	      noncorporeal(ptr) || slithy(ptr) || can_fog(mon))) return 1;
+
+    /* lugging too much junk? */
+    amt = (mon == &youmonst) ? inv_weight() + weight_cap() :
+		curr_mon_load(mon);
+    if (amt > 600) return 2;
+
+    /* Sokoban restriction applies to hero only */
+    if (mon == &youmonst && In_sokoban(&u.uz)) return 3;
+
+    /* can squeeze through */
+    return 0;
+}
+
 boolean
 invocation_pos(x, y)
 xchar x, y;
@@ -623,20 +650,18 @@ int mode;
     if (dx && dy
 	    && bad_rock(youmonst.data,ux,y) && bad_rock(youmonst.data,x,uy)) {
 	/* Move at a diagonal. */
-	if (In_sokoban(&u.uz)) {
-	    if (mode == DO_MOVE)
-		You("cannot pass that way.");
+	switch (cant_squeeze_thru(&youmonst)) {
+	case 3:
+	    if (mode == DO_MOVE) You("cannot pass that way.");
 	    return FALSE;
-	}
-	if (bigmonst(youmonst.data)) {
-	    if (mode == DO_MOVE)
-		Your("body is too large to fit through.");
+	case 2:
+	    if (mode == DO_MOVE) You("are carrying too much to get through.");
 	    return FALSE;
-	}
-	if (invent && (inv_weight() + weight_cap() > 600)) {
-	    if (mode == DO_MOVE)
-		You("are carrying too much to get through.");
+	case 1:
+	    if (mode == DO_MOVE) Your("body is too large to fit through.");
 	    return FALSE;
+	default:
+	    break;      /* can squeeze through */
 	}
     }
     /* Pick travel path that does not require crossing a trap.
diff --git a/src/mon.c b/src/mon.c
index 635ca9078..b064c34ae 100644
--- a/src/mon.c
+++ b/src/mon.c
@@ -1051,8 +1051,7 @@ nexttry:	/* eels prefer the water, but if there is no water nearby,
 	       !((IS_TREE(ntyp) ? treeok : rockok) && may_dig(nx,ny))) continue;
 	    /* KMH -- Added iron bars */
 	    if (ntyp == IRONBARS && !(flag & ALLOW_BARS)) continue;
-	    if(IS_DOOR(ntyp) && 
-		!(amorphous(mdat) || (!amorphous(mdat) && can_fog(mon))) &&
+	    if(IS_DOOR(ntyp) && !(amorphous(mdat) || can_fog(mon)) &&
 	       ((levl[nx][ny].doormask & D_CLOSED && !(flag & OPENDOOR)) ||
 		(levl[nx][ny].doormask & D_LOCKED && !(flag & UNLOCKDOOR))) &&
 	       !thrudoor) continue;
@@ -1151,9 +1150,9 @@ nexttry:	/* eels prefer the water, but if there is no water nearby,
 			if(flag & NOTONL) continue;
 			info[cnt] |= NOTONL;
 		}
-		if (nx != x && ny != y && bad_rock(mdat, x, ny)
-			    && bad_rock(mdat, nx, y)
-			    && (bigmonst(mdat) || (curr_mon_load(mon) > 600)))
+		/* check for diagonal tight squeeze */
+		if (nx != x && ny != y && bad_rock(mdat, x, ny) &&
+			    bad_rock(mdat, nx, y) && cant_squeeze_thru(mon))
 			continue;
 		/* The monster avoids a particular type of trap if it's familiar
 		 * with the trap type.  Pets get ALLOW_TRAPS and checking is