diff --git a/config/permission_groups.lua b/config/permission_groups.lua
index 60e60ae5..d171bdcc 100644
--- a/config/permission_groups.lua
+++ b/config/permission_groups.lua
@@ -112,12 +112,17 @@ local function assign_group(player)
     end
 end
 
-Event.add('on_player_joined_game',function(event)
+Event.add(defines.events.on_player_joined_game,function(event)
     local player = Game.get_player_by_index(event.player_index)
     assign_group(player)
 end)
 
-Event.add({'on_player_promoted','on_player_demoted'},function(event)
+Event.add(defines.events.on_player_promoted,function(event)
+    local player = Game.get_player_by_index(event.player_index)
+    assign_group(player)
+end)
+
+Event.add(defines.events.on_player_demoted,function(event)
     local player = Game.get_player_by_index(event.player_index)
     assign_group(player)
 end)