MariaDB v5.5.40 can't load "server_audit" plugin.

Can't load "server_audit.so" which is under "/usr/lib64/mysql/plugin" and installed by "MariaDB-5.5.40-centos6-x86_64-server.rpm".

The error messages in err.log is as below.
ERROR 1126 (HY000): Can't open shared library 'server_audit.so' (errno: 1, Loading of beta plugin SERVER_AUDIT is prohibited by --plugin-maturity=gamma)

Download, replace (the original so file), and test audit plugin v1.1.1 ~ v1.1.8 with command "install plugin server_audit soname 'server_audit.so';".
All failed as below.

[Non-debug so file, v1.1.1]
ERROR 1126 (HY000): Can't open shared library 'server_audit.so' (errno: 1, Loading of alpha plugin SERVER_AUDIT is prohibited by --plugin-maturity=gamma)
[Non-debug so file, v1.1.2~v1.1.8]
ERROR 1126 (HY000): Can't open shared library 'server_audit.so' (errno: 1, Loading of beta plugin SERVER_AUDIT is prohibited by --plugin-maturity=gamma)

[Debug so file, v1.1.1~v1.1.8 except v1.1.6]
ERROR 1126 (HY000): Can't open shared library '/usr/lib64/mysql/plugin/server_audit.so' (errno: 2, undefined symbol: safe_mutex_init)

[Debug so file, v1.1.6]
ERROR 1126 (HY000): Can't open shared library '/usr/lib64/mysql/plugin/server_audit.so' (errno: 2, undefined symbol: safe_mutex_lock)