diff --git a/src/do.c b/src/do.c
index 43376b529..1baddb56e 100644
--- a/src/do.c
+++ b/src/do.c
@@ -74,6 +74,7 @@ boulder_hits_pool(
                 levl[rx][ry].drawbridgemask &= ~DB_UNDER; /* clear lava */
                 levl[rx][ry].drawbridgemask |= DB_FLOOR;
             } else {
+                unblock_point(rx, ry);
                 levl[rx][ry].typ = ROOM, levl[rx][ry].flags = 0;
             }
             /* 3.7: normally DEADMONSTER() is used when traversing the fmon