diff --git a/src/lang/english_US.txt b/src/lang/english_US.txt
--- a/src/lang/english_US.txt
+++ b/src/lang/english_US.txt
@@ -993,6 +993,7 @@ STR_GAME_OPTIONS_AUTOSAVE_DROPDOWN_EVERY
 
 STR_GAME_OPTIONS_LANGUAGE                                       :{BLACK}Language
 STR_GAME_OPTIONS_LANGUAGE_TOOLTIP                               :{BLACK}Select the interface language to use
+STR_GAME_OPTIONS_LANGUAGE_PERCENTAGE                            :{STRING} ({NUM}% completed)
 
 STR_GAME_OPTIONS_FULLSCREEN                                     :{BLACK}Fullscreen
 STR_GAME_OPTIONS_FULLSCREEN_TOOLTIP                             :{BLACK}Check this box to play OpenTTD fullscreen mode
diff --git a/src/lang/spanish_MX.txt b/src/lang/spanish_MX.txt
--- a/src/lang/spanish_MX.txt
+++ b/src/lang/spanish_MX.txt
@@ -994,6 +994,7 @@ STR_GAME_OPTIONS_AUTOSAVE_DROPDOWN_EVERY
 
 STR_GAME_OPTIONS_LANGUAGE                                       :{BLACK}Idioma
 STR_GAME_OPTIONS_LANGUAGE_TOOLTIP                               :{BLACK}Elegir el idioma de la interfaz
+STR_GAME_OPTIONS_LANGUAGE_PERCENTAGE                            :{STRING} ({NUM}% completado)
 
 STR_GAME_OPTIONS_FULLSCREEN                                     :{BLACK}Pantalla completa
 STR_GAME_OPTIONS_FULLSCREEN_TOOLTIP                             :{BLACK}Jugar OpenTTD en pantalla completa