diff --git a/etc/ironic/ironic.conf.sample b/etc/ironic/ironic.conf.sample
index ab0d663541..cb4ec914dc 100644
--- a/etc/ironic/ironic.conf.sample
+++ b/etc/ironic/ironic.conf.sample
@@ -712,7 +712,8 @@
 #heartbeat_interval = 10
 
 # URL of Ironic API service. If not set ironic can get the
-# current value from the keystone service catalog. (string
+# current value from the keystone service catalog. If set, the
+# value must start with either http:// or https://. (string
 # value)
 #api_url = <None>
 
@@ -2300,6 +2301,11 @@
 # Minimum value: 5
 #default_notify_timeout = 30
 
+# The duration to schedule a purge of idle sender links.
+# Detach link after expiry. (integer value)
+# Minimum value: 1
+#default_sender_link_timeout = 600
+
 # Indicates the addressing mode used by the driver.
 # Permitted values:
 # 'legacy'   - use legacy non-routable addressing
diff --git a/ironic/conf/conductor.py b/ironic/conf/conductor.py
index 9ccad33e39..5eeee0f1e9 100644
--- a/ironic/conf/conductor.py
+++ b/ironic/conf/conductor.py
@@ -29,9 +29,11 @@ opts = [
                default=10,
                help=_('Seconds between conductor heart beats.')),
     cfg.StrOpt('api_url',
+               regex='^http(s?):\/\/.+',
                help=_('URL of Ironic API service. If not set ironic can '
                       'get the current value from the keystone service '
-                      'catalog.')),
+                      'catalog. If set, the value must start with either '
+                      'http:// or https://.')),
     cfg.IntOpt('heartbeat_timeout',
                default=60,
                help=_('Maximum time (in seconds) since the last check-in '
diff --git a/ironic/tests/unit/drivers/modules/test_deploy_utils.py b/ironic/tests/unit/drivers/modules/test_deploy_utils.py
index bc50db6a79..f3c5a4abdb 100644
--- a/ironic/tests/unit/drivers/modules/test_deploy_utils.py
+++ b/ironic/tests/unit/drivers/modules/test_deploy_utils.py
@@ -1588,19 +1588,19 @@ class AgentMethodsTestCase(db_base.DbTestCase):
         self._test_tear_down_inband_cleaning(manage_boot=False)
 
     def test_build_agent_options_conf(self):
-        self.config(api_url='api-url', group='conductor')
+        self.config(api_url='https://api-url', group='conductor')
         options = utils.build_agent_options(self.node)
-        self.assertEqual('api-url', options['ipa-api-url'])
+        self.assertEqual('https://api-url', options['ipa-api-url'])
         self.assertEqual(0, options['coreos.configdrive'])
 
     @mock.patch.object(utils, '_get_ironic_session')
     def test_build_agent_options_keystone(self, session_mock):
         self.config(api_url=None, group='conductor')
         sess = mock.Mock()
-        sess.get_endpoint.return_value = 'api-url'
+        sess.get_endpoint.return_value = 'https://api-url'
         session_mock.return_value = sess
         options = utils.build_agent_options(self.node)
-        self.assertEqual('api-url', options['ipa-api-url'])
+        self.assertEqual('https://api-url', options['ipa-api-url'])
         self.assertEqual(0, options['coreos.configdrive'])
 
 
diff --git a/releasenotes/notes/check_protocol_for_ironic_api-32f35c93a140d3ae.yaml b/releasenotes/notes/check_protocol_for_ironic_api-32f35c93a140d3ae.yaml
new file mode 100644
index 0000000000..4c9f6e4c7d
--- /dev/null
+++ b/releasenotes/notes/check_protocol_for_ironic_api-32f35c93a140d3ae.yaml
@@ -0,0 +1,8 @@
+---
+fixes:
+  - Accepting ``[conductor]/api_url`` value specified in the configuration
+    file that does not start with either ``https://`` or ``http://``.
+    Such value leads to deployment failure on ironic-python-agent side.
+    This misconfiguration will be detected during ironic-conductor
+    and ironic-api start. An exception will be raised and an error about
+    the invalid value will be logged.