diff --git a/.config/i3/config_common b/.config/i3/config_common
index 5a6a882..5875fac 100644
--- a/.config/i3/config_common
+++ b/.config/i3/config_common
@@ -221,7 +221,7 @@ bindsym Control+$mod+g exec dunstctl context
 ##################################
 
 # some windows will float automatically
-for_window [class="Thunderbird"] floating enable
+for_window [class="(?i)Thunderbird"] floating enable
 for_window [window_role="Steam"] floating enable
 for_window [window_role="About"] floating enable
 for_window [window_role="Organizer"] floating enable