Index: trunk/psModules/src/concepts/pmConceptsRead.c
===================================================================
--- trunk/psModules/src/concepts/pmConceptsRead.c	(revision 12521)
+++ trunk/psModules/src/concepts/pmConceptsRead.c	(revision 12619)
@@ -82,5 +82,5 @@
             psWarning("Unable to parse concept %s, but concept not marked as required.\n", spec->blank->name);
             psErrorClear();
-	    return true; // XXX return?
+            return true; // XXX return?
         }
     }
@@ -321,6 +321,8 @@
                 if (keys->n == 1) {
                     // Only one key --- proceed as usual
-                    headerItem = psMetadataLookup(hduLow->header, keywords);
-                    if (!headerItem && hduHigh != hduLow) {
+                    if (hduLow->header) {
+                        headerItem = psMetadataLookup(hduLow->header, keywords);
+                    }
+                    if (!headerItem && hduHigh != hduLow && hduHigh->header) {
                         headerItem = psMetadataLookup(hduHigh->header, keywords);
                     }