Index: trunk/psModules/src/objects/pmPSFtryFitEXT.c
===================================================================
--- trunk/psModules/src/objects/pmPSFtryFitEXT.c	(revision 30621)
+++ trunk/psModules/src/objects/pmPSFtryFitEXT.c	(revision 33586)
@@ -73,4 +73,12 @@
             continue;
         }
+        // If mask object does not exist, mark the source as bad.
+        // We cannot proceed with it because psImageMaskPixels leaves an uncleared error code last which causes
+        // psphot to exit with a fault. 
+        if (source->maskObj == NULL) {
+            psTrace ("psModules.objects", 4, "source %d (%d,%d) : null maskObj\n", i, source->peak->x, source->peak->y);
+            psfTry->mask->data.PS_TYPE_VECTOR_MASK_DATA[i] = PSFTRY_MASK_EXT_FAIL;
+            continue;
+        }
 
         source->modelEXT = pmSourceModelGuess (source, options->type);
@@ -89,5 +97,5 @@
 
         // clear object mask to define valid pixels
-	psImageMaskPixels (source->maskObj, "AND", PS_NOT_IMAGE_MASK(markVal)); // clear the circular mask
+        psImageMaskPixels (source->maskObj, "AND", PS_NOT_IMAGE_MASK(markVal)); // clear the circular mask
 
         // exclude the poor fits