diff --git a/tangostationcontrol/tangostationcontrol/devices/lofar_device.py b/tangostationcontrol/tangostationcontrol/devices/lofar_device.py
index 0e9b99ef3ddeb49e9e9f074d66890aa2a6c47aa1..068c9cee675f57f8a503fe8f4036bc2e98b80433 100644
--- a/tangostationcontrol/tangostationcontrol/devices/lofar_device.py
+++ b/tangostationcontrol/tangostationcontrol/devices/lofar_device.py
@@ -106,7 +106,7 @@ class lofar_device(Device, metaclass=DeviceMeta):
 
     # TODO(Corne): Actually implement locking in L2SS-940
     def atomic_read_modify_write_attribute(
-        self, values: List[any], proxy: DeviceProxy, attribute: str, sparse=None
+        self, values: numpy.ndarray, proxy: DeviceProxy, attribute: str, sparse=None
     ):
         """Atomatically read-modify-write the attribute on the given proxy"""