diff --git a/doc/fixes34.4 b/doc/fixes34.4
index 80ad4a52f..1c1226ad1 100644
--- a/doc/fixes34.4
+++ b/doc/fixes34.4
@@ -231,6 +231,8 @@ specifying role and/or race along with an invalid alignment for it/them in
 	mentioned the rejected alignment when asking player to pick alignment
 temple donation can recover protection previously stolen by attrcurse attack
 	even when protection amount is so big that no increment would be given
+display the invisible monster glyph ('I') whenever an unseen monster forces
+	poly'd hero out of hiding
 
 
 Platform- and/or Interface-Specific Fixes
diff --git a/src/mhitu.c b/src/mhitu.c
index 7e62f4c27..d0f1a3ba4 100644
--- a/src/mhitu.c
+++ b/src/mhitu.c
@@ -343,6 +343,7 @@ mattacku(mtmp)
 #endif
 
 	if (u.uundetected && !range2 && foundyou && !u.uswallow) {
+		if (!canspotmon(mtmp)) map_invisible(mtmp->mx, mtmp->my);
 		u.uundetected = 0;
 		if (is_hider(youmonst.data) && u.umonnum != PM_TRAPPER) {
 		    coord cc; /* maybe we need a unexto() function? */
@@ -420,8 +421,10 @@ mattacku(mtmp)
 		}
 		return(0);
 	}
+
 	if (youmonst.data->mlet == S_MIMIC && youmonst.m_ap_type &&
 		    !range2 && foundyou && !u.uswallow) {
+		if (!canspotmon(mtmp)) map_invisible(mtmp->mx, mtmp->my);
 		if (!youseeit) pline("It gets stuck on you.");
 		else pline("Wait, %s!  That's a %s named %s!",
 			   m_monnam(mtmp), youmonst.data->mname, plname);
@@ -434,6 +437,7 @@ mattacku(mtmp)
 
 	/* player might be mimicking an object */
 	if (youmonst.m_ap_type == M_AP_OBJECT && !range2 && foundyou && !u.uswallow) {
+	    if (!canspotmon(mtmp)) map_invisible(mtmp->mx, mtmp->my);
 	    if (!youseeit)
 		 pline("%s %s!", Something,
 			(likes_gold(mtmp->data) && youmonst.mappearance == GOLD_PIECE) ?