diff -up a/common/game.h.me b/common/game.h
--- a/common/game.h.me	2020-02-06 12:05:24.472403768 +0100
+++ b/common/game.h	2020-02-06 12:05:45.662644226 +0100
@@ -137,7 +137,7 @@ typedef enum {
 typedef void (*WriteLineFunc) (gpointer user_data, const gchar *);
 
 /** Default style for a player. */
-const gchar *default_player_style;
+extern const gchar *default_player_style;
 
 GameParams *params_new(void);
 GameParams *params_copy(const GameParams * params);