diff --git a/sway/behaviours b/sway/behaviours
index 53600ee1e..faeadfcf5 100644
--- a/sway/behaviours
+++ b/sway/behaviours
@@ -7,7 +7,7 @@
 assign [class="Mattermost"] 1
 assign [class="Rocket.Chat"] 1
 assign [class="UXTerm"] grave
-assign [app_id="thunderbird"] 2
+assign [class="Thunderbird"] 2
 assign [class="Chromium"] 3
 assign [class="Linphone"] 5
 assign [class="firefox"] 7