Index: trunk/pswarp/src/pswarpDefineLayout.c
===================================================================
--- trunk/pswarp/src/pswarpDefineLayout.c	(revision 35563)
+++ trunk/pswarp/src/pswarpDefineLayout.c	(revision 35684)
@@ -40,4 +40,7 @@
     // chips are not processed unless we have determined they overlap the inputs
     pmFPAExcludeChips (output->fpa);
+    if (bkgModel) {
+        pmFPAExcludeChips (bkgModel->fpa);
+    }
 
     int nInputs = psMetadataLookupS32(&status, config->arguments, "NUM_INPUTS");