diff --git a/sway/config b/sway/config
index 1f47b1c..5dc6b05 100644
--- a/sway/config
+++ b/sway/config
@@ -47,6 +47,7 @@ exec amixer set Capture nocap
 
 # prevent locking when fullscreen
 for_window [app_id="firefox"] inhibit_idle fullscreen
+for_window [class="Firefox"] inhibit_idle fullscreen
 for_window [title="VLC media player"] inhibit_idle fullscreen
 for_window [app_id="evince"] inhibit_idle fullscreen