--- a/testing/mozharness/mozharness/mozilla/testing/try_tools.py
+++ b/testing/mozharness/mozharness/mozilla/testing/try_tools.py
@@ -71,29 +71,30 @@ class TryToolsMixin(TransferMixin):
             'devtools-chrome',
             'mochitest',
             'reftest',
         )),
     }
 
     def _extract_try_message(self):
         msg = None
+        buildbot_config = self.buildbot_config or {}
         if "try_message" in self.config and self.config["try_message"]:
             msg = self.config["try_message"]
         elif 'TRY_COMMIT_MSG' in os.environ:
             msg = os.environ['TRY_COMMIT_MSG']
         elif self._is_try():
-            if self.buildbot_config['sourcestamp']['changes']:
-                msg = self.buildbot_config['sourcestamp']['changes'][-1]['comments']
+            if 'sourcestamp' in buildbot_config and buildbot_config['sourcestamp'].get('changes'):
+                msg = buildbot_config['sourcestamp']['changes'][-1].get('comments')
 
             if msg is None or len(msg) == 1024:
                 # This commit message was potentially truncated or not available in
                 # buildbot_config (e.g. if running in TaskCluster), get the full message
                 # from hg.
-                props = self.buildbot_config['properties']
+                props = buildbot_config.get('properties', {})
                 repo_url = 'https://hg.mozilla.org/%s/'
                 if 'revision' in props and 'repo_path' in props:
                     rev = props['revision']
                     repo_path = props['repo_path']
                 else:
                     # In TaskCluster we have no buildbot props, rely on env vars instead
                     rev = os.environ.get('GECKO_HEAD_REV')
                     repo_path = self.config.get('branch')
@@ -107,20 +108,20 @@ class TryToolsMixin(TransferMixin):
 
                 url = '{}json-pushes?changeset={}&full=1'.format(repo_url, rev)
 
                 pushinfo = self.load_json_from_url(url)
                 for k, v in pushinfo.items():
                     if isinstance(v, dict) and 'changesets' in v:
                         msg = v['changesets'][-1]['desc']
 
-            if not msg and 'try_syntax' in self.buildbot_config['properties']:
+            if not msg and 'try_syntax' in buildbot_config.get('properties', {}):
                 # If we don't find try syntax in the usual place, check for it in an
                 # alternate property available to tools using self-serve.
-                msg = self.buildbot_config['properties']['try_syntax']
+                msg = buildbot_config['properties']['try_syntax']
         if not msg:
             self.warning('Try message not found.')
         return msg
 
     def _extract_try_args(self, msg):
         """ Returns a list of args from a try message, for parsing """
         if not msg:
             return None

--- a/testing/mozharness/scripts/fx_desktop_build.py
+++ b/testing/mozharness/scripts/fx_desktop_build.py
@@ -119,19 +119,19 @@ class FxDesktopBuild(BuildScript, TryToo
                     platform_for_log_url += '-pgo'
                 # postrun.py uses stage_platform buildbot prop as part of the log url
                 self.set_buildbot_property('stage_platform',
                                            platform_for_log_url,
                                            write_to_file=True)
             else:
                 self.fatal("'stage_platform' not determined and is required in your config")
 
-            if self.try_message_has_flag('artifact'):
-                self.info('Artifact build requested in try syntax.')
-                self._update_build_variant(rw_config)
+        if self.try_message_has_flag('artifact'):
+            self.info('Artifact build requested in try syntax.')
+            self._update_build_variant(rw_config)
 
     # helpers
     def _update_build_variant(self, rw_config, variant='artifact'):
         """ Intended for use in _pre_config_lock """
         c = self.config
         variant_cfg_path, _ = BuildOptionParser.find_variant_cfg_path(
             '--custom-build-variant-cfg',
             variant,