diff --git a/hooks/percona_hooks.py b/hooks/percona_hooks.py
index 2758a14..25fc81c 100755
--- a/hooks/percona_hooks.py
+++ b/hooks/percona_hooks.py
@@ -26,6 +26,7 @@ from charmhelpers.core.hookenv import (
     network_get_primary_address,
     charm_name,
     leader_get,
+    open_port,
 )
 from charmhelpers.core.host import (
     service_restart,
@@ -96,6 +97,7 @@ from percona_utils import (
     get_cluster_host_ip,
     client_node_is_ready,
     leader_node_is_ready,
+    DEFAULT_MYSQL_PORT,
 )
 
 
@@ -296,6 +298,8 @@ def config_changed():
     if is_relation_made('nrpe-external-master'):
         update_nrpe_config()
 
+    open_port(DEFAULT_MYSQL_PORT)
+
 
 @hooks.hook('cluster-relation-joined')
 def cluster_joined():
diff --git a/hooks/percona_utils.py b/hooks/percona_utils.py
index 3a4f22c..6b9ee07 100644
--- a/hooks/percona_utils.py
+++ b/hooks/percona_utils.py
@@ -65,6 +65,7 @@ REPO = """deb http://repo.percona.com/apt {release} main
 deb-src http://repo.percona.com/apt {release} main"""
 SEEDED_MARKER = "{data_dir}/seeded"
 HOSTS_FILE = '/etc/hosts'
+DEFAULT_MYSQL_PORT = 3306
 
 # NOTE(ajkavanagh) - this is 'required' for the pause/resume code for
 # maintenance mode, but is currently not populated as the
diff --git a/unit_tests/test_percona_hooks.py b/unit_tests/test_percona_hooks.py
index 2181750..ed8dd02 100644
--- a/unit_tests/test_percona_hooks.py
+++ b/unit_tests/test_percona_hooks.py
@@ -206,3 +206,38 @@ class TestNRPERelation(CharmTestCase):
         hooks.update_nrpe_config()
         self.nrpe.add_init_service_checks.assert_called_once_with(
             mock.ANY, ["mysql"], mock.ANY)
+
+
+class TestConfigChanged(CharmTestCase):
+
+    TO_PATCH = [
+        'log',
+        'open_port',
+        'config',
+        'is_unit_paused_set',
+        'get_cluster_hosts',
+        'is_bootstrapped',
+        'is_leader',
+        'render_config_restart_on_changed',
+        'update_shared_db_rels',
+        'install_mysql_ocf',
+        'relation_ids',
+        'is_relation_made',
+        'ha_relation_joined',
+        'update_nrpe_config',
+        'assert_charm_supports_ipv6',
+    ]
+
+    def setUp(self):
+        CharmTestCase.setUp(self, hooks, self.TO_PATCH)
+        self.config.side_effect = self.test_config.get
+
+    def test_config_changed_open_port(self):
+        '''Ensure open_port is called with MySQL default port'''
+        self.is_unit_paused_set.return_value = False
+        self.is_bootstrapped.return_value = False
+        self.is_leader.return_value = False
+        self.relation_ids.return_value = []
+        self.is_relation_made.return_value = False
+        hooks.config_changed()
+        self.open_port.assert_called_with(3306)