diff --git a/geomagio/TimeseriesFactory.py b/geomagio/TimeseriesFactory.py
index 644b44b5c5d36d4fd70e76c226be6dbf96bd1748..eb38272f9f320f0ad8a12257e5e44cd5c7099c70 100644
--- a/geomagio/TimeseriesFactory.py
+++ b/geomagio/TimeseriesFactory.py
@@ -192,7 +192,10 @@ class TimeseriesFactory(object):
         interval = interval or self.interval
 
         timeseries = obspy.core.Stream()
-        urlIntervals = Util.get_intervals(starttime, endtime, self.urlInterval)
+        urlIntervals = Util.get_intervals(
+                starttime=starttime,
+                endtime=endtime,
+                size=self.urlInterval)
         for urlInterval in urlIntervals:
             url = self._get_url(
                     observatory=observatory,