diff --git a/SAS/TMSS/backend/src/tmss/tmssapp/adapters/parset.py b/SAS/TMSS/backend/src/tmss/tmssapp/adapters/parset.py
index f19b68b2bbe628736e10d48f7abc5ddb499aee8f..313aaf8090155c185fcc8ee7b62243dd52c8f74b 100644
--- a/SAS/TMSS/backend/src/tmss/tmssapp/adapters/parset.py
+++ b/SAS/TMSS/backend/src/tmss/tmssapp/adapters/parset.py
@@ -514,6 +514,10 @@ def _convert_to_parset_dict_for_pipelinecontrol_schema(subtask: models.Subtask)
         parset["Observation.ObservationControl.PythonControl.DPPP.demixer.subtractsources"] = ""
         parset["Observation.ObservationControl.PythonControl.DPPP.demixer.targetsource"] = ""
         parset["Observation.ObservationControl.PythonControl.DPPP.demixer.type"] = "demixer"
+    else:
+        # ResourceEstimator wants these keys always
+        parset["Observation.ObservationControl.PythonControl.DPPP.demixer.freqstep"] = 1
+        parset["Observation.ObservationControl.PythonControl.DPPP.demixer.timestep"] = 1
 
     parset["Observation.ObservationControl.PythonControl.DPPP.steps"] = "[%s]" % ",".join(dppp_steps)
     parset["Observation.ObservationControl.PythonControl.DPPP.msout.storagemanager.name"] = spec["storagemanager"]