diff --git a/python/lsst/drp/tasks/assemble_coadd.py b/python/lsst/drp/tasks/assemble_coadd.py
index 09ef94db..6d3e2d75 100644
--- a/python/lsst/drp/tasks/assemble_coadd.py
+++ b/python/lsst/drp/tasks/assemble_coadd.py
@@ -1580,6 +1580,11 @@ def _makeSupplementaryData(self, butlerQC, inputRefs, outputRefs):
         staticSkyModelInputRefs = copy.deepcopy(inputRefs)
         staticSkyModelInputRefs.inputWarps = inputRefs.psfMatchedWarps
 
+        # self.assembleStaticSkyModel is not expecting psfMatchedWarps as
+        # input. But in its runQuantum, ButlerQC would try to be helpful and
+        # read all of them in to memory.
+        del staticSkyModelInputRefs.psfMatchedWarps
+
         # Because subtasks don't have connections we have to make one.
         # The main task's `templateCoadd` is the subtask's `coaddExposure`
         staticSkyModelOutputRefs = copy.deepcopy(outputRefs)