diff --git a/src/do.c b/src/do.c
index 00b9b72b2..aeba44118 100644
--- a/src/do.c
+++ b/src/do.c
@@ -52,6 +52,8 @@ boulder_hits_pool(struct obj *otmp, int rx, int ry, boolean pushing)
         const char *what = waterbody_name(rx, ry);
         schar ltyp = levl[rx][ry].typ;
         int chance = rn2(10); /* water: 90%; lava: 10% */
+        struct monst *mtmp;
+
         fills_up = lava ? chance == 0 : chance != 0;
 
         if (fills_up) {
@@ -63,6 +65,9 @@ boulder_hits_pool(struct obj *otmp, int rx, int ry, boolean pushing)
             } else
                 levl[rx][ry].typ = ROOM, levl[rx][ry].flags = 0;
 
+            if ((mtmp = m_at(rx, ry)) != 0)
+                mondied(mtmp);
+
             if (ttmp)
                 (void) delfloortrap(ttmp);
             bury_objs(rx, ry);