diff --git a/doc/fixes34.4 b/doc/fixes34.4
index 0448c2643..33eb87839 100644
--- a/doc/fixes34.4
+++ b/doc/fixes34.4
@@ -277,6 +277,8 @@ wielding a cloak of magic resistance or gray dragon scales, or carrying one in
 	to polymorphed hero
 wielding a potion of blindness or carrying one in alternate weapon or quiver
 	slot conferred resistance against light-based blindness to any hero
+zapping closing or breaking magic up or down from beneath an open drawbridge's
+	portcullis failed if bridge orientation was north-to-south (Valk quest)
 
 
 Platform- and/or Interface-Specific Fixes
diff --git a/src/zap.c b/src/zap.c
index dbfbcba54..27b71c6ea 100644
--- a/src/zap.c
+++ b/src/zap.c
@@ -2495,7 +2495,7 @@ struct obj *obj;	/* wand or spell */
 	case SPE_WIZARD_LOCK:
 	    /* down at open bridge or up or down at open portcullis */
 	    if (((levl[x][y].typ == DRAWBRIDGE_DOWN) ? (u.dz > 0) :
-			(is_drawbridge_wall(x,y) && !is_db_wall(x,y))) &&
+			(is_drawbridge_wall(x,y) >= 0 && !is_db_wall(x,y))) &&
 		    find_drawbridge(&xx, &yy)) {
 		if (!striking)
 		    close_drawbridge(xx, yy);