Index: trunk/psModules/src/imcombine/pmSubtractionMatch.c
===================================================================
--- trunk/psModules/src/imcombine/pmSubtractionMatch.c	(revision 24181)
+++ trunk/psModules/src/imcombine/pmSubtractionMatch.c	(revision 24257)
@@ -246,5 +246,5 @@
                                          badFrac, mode); // Subtraction mask
     if (!subMask) {
-        psError(PS_ERR_UNKNOWN, false, "Unable to generate subtraction mask.");
+        psError(psErrorCodeLast(), false, "Unable to generate subtraction mask.");
         psFree(kernels);
         psFree(regions);