--- a/testing/mozharness/mozharness/mozilla/building/buildbase.py
+++ b/testing/mozharness/mozharness/mozilla/building/buildbase.py
@@ -1992,17 +1992,17 @@ or run without that action (ie: --no-{ac
                 "alertThreshold": 0.25,
                 "subtests": size_measurements
             })
 
         build_metrics = self._load_build_resources()
         if build_metrics:
             perfherder_data['suites'].append(build_metrics)
 
-        if self.query_is_nightly:
+        if self.query_is_nightly():
             for suite in perfherder_data['suites']:
                 if 'extraOptions' in suite:
                     suite['extraOptions'] = ['nightly'] + suite['extraOptions']
                 else:
                     suite['extraOptions'] = ['nightly']
 
         if perfherder_data["suites"]:
             self.info('PERFHERDER_DATA: %s' % json.dumps(perfherder_data))