diff --git a/defaults/main.yml b/defaults/main.yml
index 1a0da7f..68dd2ee 100644
--- a/defaults/main.yml
+++ b/defaults/main.yml
@@ -44,7 +44,7 @@ mysql_thread_concurrency: 2
 # InnoDB settings.
 mysql_innodb_file_per_table: '1'
 mysql_innodb_buffer_pool_size: "{{ (ansible_memtotal_mb * 0.6) | round | int }}M"
-mysql_innodb_additional_mem_pool_size: '20M'
+mysql_innodb_additional_mem_pool_size: '20M' # See: http://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html#sysvar_innodb_additional_mem_pool_size
 mysql_innodb_log_file_size: '64M'
 mysql_innodb_log_buffer_size: '8M'
 mysql_innodb_flush_log_at_trx_commit: '1'
diff --git a/templates/etc/mysql/my.cnf.j2 b/templates/etc/mysql/my.cnf.j2
index e4696b8..11d9c7e 100644
--- a/templates/etc/mysql/my.cnf.j2
+++ b/templates/etc/mysql/my.cnf.j2
@@ -63,7 +63,9 @@ thread_concurrency = {{ mysql_thread_concurrency }}
 # InnoDB settings.
 innodb_file_per_table = {{ mysql_innodb_file_per_table }}
 innodb_buffer_pool_size = {{ mysql_innodb_buffer_pool_size }}
+{% if mysql_innodb_additional_mem_pool_size is defined %}
 innodb_additional_mem_pool_size = {{ mysql_innodb_additional_mem_pool_size }}
+{% endif %}
 # It craches after install (mysql 5.5)... TODO FIX -> http://dev.mysql.com/doc/refman/5.6/en/innodb-data-log-reconfiguration.html
 #innodb_log_file_size = {{ mysql_innodb_log_file_size }}
 #innodb_log_buffer_size = {{ mysql_innodb_log_buffer_size }}