diff --git a/sway/config b/sway/config
index f7b28fa..1bcd940 100644
--- a/sway/config
+++ b/sway/config
@@ -77,7 +77,7 @@ for_window [app_id="org.gnome.NautilusPreviewer"] floating enable
 
 # Stick windows to workspaces
 assign [app_id="NewsFlashGTK"] 8
-assign [class="Thunderbird"] 9
+assign [app_id="thunderbird"] 9
 assign [app_id="evolution"] 9
 assign [app_id="rhythmbox"] 10
 assign [app_id="lollypop"] 10