diff --git a/i3/layouts/left.json b/i3/layouts/left.json
index a811545..254062b 100644
--- a/i3/layouts/left.json
+++ b/i3/layouts/left.json
@@ -98,7 +98,7 @@
                     "percent": 1,
                     "swallows": [
                        {
-                       "class": "^Thunderbird$"
+                       "class": "^thunderbird$"
                        }
                     ],
                     "type": "con"