Index: trunk/magic/remove/src/diffedpixels.c
===================================================================
--- trunk/magic/remove/src/diffedpixels.c	(revision 26890)
+++ trunk/magic/remove/src/diffedpixels.c	(revision 27102)
@@ -37,5 +37,8 @@
         psString filename = psArrayGet(skycells, i);
         psString resolved_name = pmConfigConvertFilename(filename, config, false, false);
-
+        if (resolved_name == NULL) {
+            psError(PS_ERR_IO, false, "failed to resolve skycell file: %s", filename);
+            streaksExit("", PS_EXIT_DATA_ERROR);
+        }
         addTouchedPixels(sf, resolved_name);
         psFree(resolved_name);