diff --git a/css/80_app.css b/css/80_app.css
index 040001c1f..9845da69d 100644
--- a/css/80_app.css
+++ b/css/80_app.css
@@ -2505,7 +2505,7 @@ img.tile {
 }
 
 img.tile-debug {
-    border: 1px solid red;
+    outline: 1px solid red;
 }
 
 img.tile-loaded {