diff --git a/mx_mysql.h b/mx_mysql.h
index 17f5a06..0bf2c81 100644
--- a/mx_mysql.h
+++ b/mx_mysql.h
@@ -77,7 +77,7 @@ struct mx_mysql_stmt {
 
 int mx_mysql_initialize(struct mx_mysql **mysql);
 
-int mx_mysql_option_set_default_file(struct mx_mysql *mysql, char *fname);
+int mx_mysql_option_set_default_file(struct mx_mysql *mysql, char *fname)  __attribute__ ((warn_unused_result));
 int mx_mysql_option_set_default_group(struct mx_mysql *mysql, char *group);
 int mx_mysql_option_set_reconnect(struct mx_mysql *mysql, int reconnect);