diff --git a/src/mthrowu.c b/src/mthrowu.c
index cf775ec7d..7f546d815 100644
--- a/src/mthrowu.c
+++ b/src/mthrowu.c
@@ -1037,7 +1037,8 @@ linedup_callback(
             bx += dx, by += dy;
             if (!isok(bx, by))
                 return FALSE;
-            if (IS_ROCK(levl[bx][by].typ) || closed_door(bx, by))
+            if (IS_ROCK(levl[bx][by].typ) || closed_door(bx, by)
+                || levl[bx][by].typ == WATER)
                 return FALSE;
             if ((*fnc)(bx, by))
                 return TRUE;
@@ -1080,7 +1081,8 @@ linedup(
         do {
             /* <bx,by> is guaranteed to eventually converge with <ax,ay> */
             bx += dx, by += dy;
-            if (IS_ROCK(levl[bx][by].typ) || closed_door(bx, by))
+            if (IS_ROCK(levl[bx][by].typ) || closed_door(bx, by)
+                || levl[bx][by].typ == WATER)
                 return FALSE;
             if (sobj_at(BOULDER, bx, by))
                 ++boulderspots;