diff --git a/tangostationcontrol/tangostationcontrol/configuration/schemas/xst.json b/tangostationcontrol/tangostationcontrol/configuration/schemas/xst.json
index 27cf2ec7849e36aa84b53a56e60a9bae3224126d..7a2b18e8d93b24811a0d58320d4a73add076c049 100644
--- a/tangostationcontrol/tangostationcontrol/configuration/schemas/xst.json
+++ b/tangostationcontrol/tangostationcontrol/configuration/schemas/xst.json
@@ -9,6 +9,7 @@
   "properties": {
     "subbands": {
       "type": "array",
+      "default": [300],
       "minItems": 0,
       "maxItems": 7,
       "items": {
diff --git a/tangostationcontrol/tangostationcontrol/devices/observation_field.py b/tangostationcontrol/tangostationcontrol/devices/observation_field.py
index 44875bd5c0a5fa710fe58eaeae7f230316714afe..e7c113233425928321ac9ea0f74c9933e60bd83f 100644
--- a/tangostationcontrol/tangostationcontrol/devices/observation_field.py
+++ b/tangostationcontrol/tangostationcontrol/devices/observation_field.py
@@ -279,7 +279,7 @@ class ObservationField(LOFARDevice):
                 dtype=numpy.uint32,
             )
         except AttributeError:
-            return numpy.array([], dtype=numpy.uint32)
+            return numpy.array([300], dtype=numpy.uint32)
 
     @attribute(
         doc="The subband indices are increased with this index every interval, causing different subbands to be emitted.",