Index: trunk/psphot/src/psphotStackUpdateReadout.c
===================================================================
--- trunk/psphot/src/psphotStackUpdateReadout.c	(revision 38515)
+++ trunk/psphot/src/psphotStackUpdateReadout.c	(revision 38531)
@@ -300,4 +300,28 @@
     maskVal |= markVal;
 
+    // This code currently assumes that all extended source models are PCM.
+    // Examine the recipe and make sure that this is true.
+    psMetadata *allModels = psMetadataLookupMetadata (&status, recipe, "EXTENDED_SOURCE_MODELS");
+    if (!status) {
+        psAssert (allModels, "failed to find list of extended source models\n");
+    }
+    psMetadataIterator *iter = psMetadataIteratorAlloc (allModels, PS_LIST_HEAD, NULL);
+    psMetadataItem *item = NULL;
+    while ((item = psMetadataGetAndIncrement (iter)) != NULL) {
+        if (item->type != PS_DATA_METADATA) {
+            psAbort ("Invalid type for EXTENDED_SOURCE_MODEL entry %s, not a metadata folder", item->name);
+        }
+        psMetadata *model = (psMetadata *) item->data.md;
+        // char *modelName = psMetadataLookupStr (&status, model, "MODEL");
+
+        char *convolvedWord = psMetadataLookupStr (&status, model, "PSF_CONVOLVED");
+        if (!status || (strcasecmp (convolvedWord, "true") && strcasecmp (convolvedWord, "false"))) {
+            psAbort ("PSF_CONVOLVED entry invalid or missing for EXTENDED_SOURCE_MODEL entry %s", item->name);
+        }
+        bool convolved = !strcasecmp (convolvedWord, "true");
+        psAssert (convolved, "EXTENDED SOURCE model %s is not convolved. This code is not ready for that\n", item->name);
+    }
+    psFree (iter);
+
     // setup the PSF fit radius details
     psphotInitRadiusPSF (recipe, readout);
@@ -343,4 +367,7 @@
             psFree(source->modelPSF) ;
             modelPSF = NULL;
+            // At least once I saw a source with an extended model but no psf model
+            psFree(source->modelEXT);
+            source->modelEXT = NULL;
         }