diff --git a/google/cloud/monitoring_v3/query.py b/google/cloud/monitoring_v3/query.py
index 95f80848..34cee9c2 100644
--- a/google/cloud/monitoring_v3/query.py
+++ b/google/cloud/monitoring_v3/query.py
@@ -443,7 +443,9 @@ def iter(self, headers_only=False, page_size=None):
             raise ValueError("Query time interval not specified.")
 
         params = self._build_query_params(headers_only, page_size)
-        for ts in self._client.list_time_series(**params):
+
+        request = monitoring_v3.ListTimeSeriesRequest(**params)
+        for ts in self._client.list_time_series(request):
             yield ts
 
     def _build_query_params(self, headers_only=False, page_size=None):
diff --git a/tests/unit/test_query.py b/tests/unit/test_query.py
index 23b47193..cf835e90 100644
--- a/tests/unit/test_query.py
+++ b/tests/unit/test_query.py
@@ -394,6 +394,10 @@ def test_iteration_headers_only(self):
         client = self._create_client(channel)
         query = self._make_one(client, PROJECT, METRIC_TYPE)
         query = query.select_interval(start_time=T0, end_time=T1)
+
+        # add a temporal alignment to test that "aggregation" query params is
+        # correctly processed
+        query = query.align(monitoring_v3.Aggregation.Aligner.ALIGN_MAX, seconds=3600)
         response = list(query.iter(headers_only=True))
 
         self.assertEqual(len(response), 2)
@@ -412,6 +416,10 @@ def test_iteration_headers_only(self):
             filter='metric.type = "{type}"'.format(type=METRIC_TYPE),
             interval=self._make_interval(T1, T0),
             view=monitoring_v3.ListTimeSeriesRequest.TimeSeriesView.HEADERS,
+            aggregation=monitoring_v3.Aggregation(
+                per_series_aligner=monitoring_v3.Aggregation.Aligner.ALIGN_MAX,
+                alignment_period={"seconds": 3600},
+            ),
         )
         request = channel.requests[0][1]
         self.assertEqual(request, expected_request)