diff --git a/jenkins_jobs/modules/helpers.py b/jenkins_jobs/modules/helpers.py
index 725da2adb..964fb4696 100644
--- a/jenkins_jobs/modules/helpers.py
+++ b/jenkins_jobs/modules/helpers.py
@@ -589,7 +589,7 @@ def trigger_project(tconfigs, project_def, param_order=None):
                     mapping, fail_required=True)
 
 
-def convert_mapping_to_xml(parent, data, mapping, fail_required=False):
+def convert_mapping_to_xml(parent, data, mapping, fail_required=True):
     """Convert mapping to XML
 
     fail_required affects the last parameter of the mapping field when it's
@@ -624,12 +624,9 @@ def convert_mapping_to_xml(parent, data, mapping, fail_required=False):
                 valid_dict = elem[3]
 
         # Use fail_required setting to allow support for optional parameters
-        # we will phase this out in the future as we rework plugins so that
-        # optional parameters use a default setting instead.
         if val is None and fail_required is True:
             raise MissingAttributeError(optname)
 
-        # (Deprecated) in the future we will default to fail_required True
         # if no value is provided then continue else leave it
         # up to the user if they want to use an empty XML tag
         if val is None and fail_required is False:
diff --git a/jenkins_jobs/modules/publishers.py b/jenkins_jobs/modules/publishers.py
index 00645b593..0cef58e68 100644
--- a/jenkins_jobs/modules/publishers.py
+++ b/jenkins_jobs/modules/publishers.py
@@ -388,7 +388,8 @@ def mqtt(registry, xml_parent, data):
                                         'EXACTLY_ONCE': '2'}),
         ('retain-message', 'retainMessage', False)
     ]
-    helpers.convert_mapping_to_xml(mqtt, data, mqtt_mapping)
+    helpers.convert_mapping_to_xml(mqtt, data, mqtt_mapping,
+                                   fail_required=False)
 
 
 def codecover(registry, xml_parent, data):