diff --git a/doc/fixes35.0 b/doc/fixes35.0
index 4d1c28bd4..cbc8589dd 100644
--- a/doc/fixes35.0
+++ b/doc/fixes35.0
@@ -142,6 +142,7 @@ don't give attribute adjustment messages ("you feel wise") unless the current
 	value actually changes
 meditating monsters stop meditating when affected by something which wakes
 	sleeping mosnters
+monsters capable of hiding can't do so when trapped or while holding you
 
 
 Platform- and/or Interface-Specific Fixes
diff --git a/src/mon.c b/src/mon.c
index 139735783..2931bacbb 100644
--- a/src/mon.c
+++ b/src/mon.c
@@ -2366,11 +2366,19 @@ boolean
 hideunder(mtmp)
 struct monst *mtmp;
 {
-	boolean undetected = FALSE;
-	xchar x = (mtmp == &youmonst) ? u.ux : mtmp->mx;
-	xchar y = (mtmp == &youmonst) ? u.uy : mtmp->my;
+	struct trap *t;
+	boolean undetected = FALSE,
+		is_u = (mtmp == &youmonst);
+	xchar x = is_u ? u.ux : mtmp->mx,
+	      y = is_u ? u.uy : mtmp->my;
 
-	if (mtmp->data->mlet == S_EEL) {
+	if (mtmp == u.ustuck) {
+	    ;	/* can't hide if holding you or held by you */
+	} else if (is_u ? (u.utrap && u.utraptype != TT_PIT) :
+			  (mtmp->mtrapped && (t = t_at(x, y)) != 0 &&
+				!(t->ttyp == PIT || t->ttyp == SPIKED_PIT))) {
+	    ;	/* can't hide while stuck in a non-pit trap */
+	} else if (mtmp->data->mlet == S_EEL) {
 	    undetected = (is_pool(x, y) && !Is_waterlevel(&u.uz));
 	} else if (hides_under(mtmp->data) && OBJ_AT(x, y)) {
 	    struct obj *otmp = level.objects[x][y];
@@ -2382,7 +2390,7 @@ struct monst *mtmp;
 		undetected = TRUE;
 	}
 
-	if (mtmp == &youmonst) u.uundetected = undetected;
+	if (is_u) u.uundetected = undetected;
 	else mtmp->mundetected = undetected;
 	return undetected;
 }
diff --git a/src/polyself.c b/src/polyself.c
index 454a09380..6cc410d5a 100644
--- a/src/polyself.c
+++ b/src/polyself.c
@@ -1,4 +1,4 @@
-/*	SCCS Id: @(#)polyself.c	3.5	2005/09/19	*/
+/*	SCCS Id: @(#)polyself.c	3.5	2006/05/26	*/
 /*	Copyright (C) 1987, 1988, 1989 by Ken Arromdee */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -1096,6 +1096,20 @@ dohide()
 {
 	boolean ismimic = youmonst.data->mlet == S_MIMIC;
 
+	if ((u.utrap && u.utraptype != TT_PIT) || u.ustuck) {
+		You_cant("hide while you're %s.",
+			 !u.ustuck ? "trapped" :
+			   !sticks(youmonst.data) ? "being held" :
+			     humanoid(u.ustuck->data) ? "holding someone" :
+			       "holding that creature");
+		if (u.uundetected ||
+			    (ismimic && youmonst.m_ap_type != M_AP_NOTHING)) {
+			u.uundetected = 0;
+			youmonst.m_ap_type = M_AP_NOTHING;
+			newsym(u.ux, u.uy);
+		}
+		return 0;
+	}
 	if (u.uundetected || (ismimic && youmonst.m_ap_type != M_AP_NOTHING)) {
 		You("are already hiding.");
 		return(0);