diff --git a/tangostationcontrol/tangostationcontrol/devices/beam.py b/tangostationcontrol/tangostationcontrol/devices/beam.py
index 1f24e804abd1469c11caf86506ac95fecb88a0ac..d62a49e368598ccf5868f5c74402233d5eb403cf 100644
--- a/tangostationcontrol/tangostationcontrol/devices/beam.py
+++ b/tangostationcontrol/tangostationcontrol/devices/beam.py
@@ -156,7 +156,7 @@ class Beam(lofar_device):
         else:
             self.HBAT_beam_tracker.stop()
 
-    def _HBAT_delays(self, pointing_direction: numpy.array, timestamp: datetime.datetime = datetime.datetime.now()):
+    def _HBAT_delays(self, pointing_direction: numpy.array, timestamp: datetime.datetime = None):
         """
         Calculate the delays (in seconds) based on the pointing list and the timestamp
         """