diff --git a/overlay/etc/chrony/chrony.conf b/overlay/etc/chrony/chrony.conf
index ce4bfcd..36e6f45 100644
--- a/overlay/etc/chrony/chrony.conf
+++ b/overlay/etc/chrony/chrony.conf
@@ -61,5 +61,6 @@ makestep 1 3
 # leap-smeared time.
 leapsectz right/UTC
 
-# ET: Enable GPS as a time source
-refclock SHM 0 refid GPS poll 4 precision 1e-3 offset 0.128
+# ET: Enable NMEA sentences from GPS as a time source. Allow for a small
+#     offset delay since PPS is not used.
+refclock SHM 0 refid NMEA poll 4 precision 1e-1 offset 0.0 delay 0.2