diff --git a/src/upgrade.py b/src/upgrade.py
index 3c9d653a75..ef69e5ac49 100644
--- a/src/upgrade.py
+++ b/src/upgrade.py
@@ -126,6 +126,10 @@ def _on_upgrade_charm_check_legacy(self) -> None:
     @override
     def _on_upgrade_granted(self, event: UpgradeGrantedEvent) -> None:
         # Refresh the charmed PostgreSQL snap and restart the database.
+        # Update the configuration.
+        self.charm.unit.status = MaintenanceStatus("updating configuration")
+        self.charm.update_config()
+
         self.charm.unit.status = MaintenanceStatus("refreshing the snap")
         self.charm._install_snap_packages(packages=SNAP_PACKAGES, refresh=True)
 
diff --git a/tests/unit/test_upgrade.py b/tests/unit/test_upgrade.py
index 9402ad1295..dd584f2899 100644
--- a/tests/unit/test_upgrade.py
+++ b/tests/unit/test_upgrade.py
@@ -62,8 +62,10 @@ def test_log_rollback(self, mock_logging, _update_config):
     @patch("charm.PostgresqlOperatorCharm._setup_exporter")
     @patch("charm.Patroni.start_patroni")
     @patch("charm.PostgresqlOperatorCharm._install_snap_packages")
+    @patch("charm.PostgresqlOperatorCharm.update_config")
     def test_on_upgrade_granted(
         self,
+        _update_config,
         _install_snap_packages,
         _start_patroni,
         _setup_exporter,
@@ -80,6 +82,7 @@ def test_on_upgrade_granted(
         mock_event = MagicMock()
         _start_patroni.return_value = False
         self.charm.upgrade._on_upgrade_granted(mock_event)
+        _update_config.assert_called_once()
         _install_snap_packages.assert_called_once_with(packages=SNAP_PACKAGES, refresh=True)
         _member_started.assert_not_called()
         mock_event.defer.assert_not_called()