diff --git a/data/gui/window/mp_login.cfg b/data/gui/window/mp_login.cfg
index 3561efa43a3..0a378d0ce09 100644
--- a/data/gui/window/mp_login.cfg
+++ b/data/gui/window/mp_login.cfg
@@ -104,6 +104,7 @@
 									id = "user_name"
 									definition = "default"
 									history = "mp_user_name_history"
+									max_input_length = 20
 								[/text_box]
 
 							[/column]