Index: trunk/ppSub/src/ppSubMatchPSFs.c
===================================================================
--- trunk/ppSub/src/ppSubMatchPSFs.c	(revision 23939)
+++ trunk/ppSub/src/ppSubMatchPSFs.c	(revision 24065)
@@ -60,6 +60,8 @@
     pmReadout *inSourceRO = pmFPAfileThisReadout(config->files, view, "PPSUB.INPUT.SOURCES");
     pmReadout *refSourceRO = pmFPAfileThisReadout(config->files, view, "PPSUB.REF.SOURCES");
-    psArray *inSources = psMetadataLookupPtr(&mdok, inSourceRO->analysis, "PSPHOT.SOURCES"); // Source list
-    psArray *refSources = psMetadataLookupPtr(&mdok, refSourceRO->analysis, "PSPHOT.SOURCES"); // Source list
+    psArray *inSources = inSourceRO ? psMetadataLookupPtr(&mdok, inSourceRO->analysis, "PSPHOT.SOURCES") :
+        NULL; // Source list from input image
+    psArray *refSources = refSourceRO ? psMetadataLookupPtr(&mdok, refSourceRO->analysis, "PSPHOT.SOURCES") :
+        NULL ; // Source list from reference image
 
     psArray *sources = NULL;            // Merged list of sources