diff --git a/lib/widgets/screen.js b/lib/widgets/screen.js
index ee71512..28ff0b5 100644
--- a/lib/widgets/screen.js
+++ b/lib/widgets/screen.js
@@ -940,6 +940,7 @@ Screen.prototype._dockBorders = function() {
       ch = lines[y][x][1];
       if (angles[ch]) {
         lines[y][x][1] = this._getAngle(lines, x, y);
+        lines[y].dirty = true;
       }
     }
   }