diff --git a/doc/fixes34.1 b/doc/fixes34.1
index 2bc548809..d699c2753 100644
--- a/doc/fixes34.1
+++ b/doc/fixes34.1
@@ -132,6 +132,7 @@ headstone writing was using the adjective "weird" when engraving with a wand
 don't report "you were riding" if you die as a result of dismounting
 allow #untrapping of chests that are co-located with floor traps and hero
 unmap "I" symbols when searching while blind and levitating
+monsters that are frozen or sleeping cannot be grateful for untrapping
 
 
 Platform- and/or Interface-Specific Fixes
diff --git a/src/trap.c b/src/trap.c
index d5cc2adf1..eafc20303 100644
--- a/src/trap.c
+++ b/src/trap.c
@@ -2886,6 +2886,7 @@ struct monst *mtmp;
 {
 	if (!ttmp->madeby_u) {
 	    if (rnl(10) < 8 && !mtmp->mpeaceful &&
+		    !mtmp->msleeping && !mtmp->mfrozen &&
 		    !mindless(mtmp->data) &&
 		    mtmp->data->mlet != S_HUMAN) {
 		mtmp->mpeaceful = 1;