Index: /trunk/ppMerge/src/ppMergeMask.c
===================================================================
--- /trunk/ppMerge/src/ppMergeMask.c	(revision 17429)
+++ /trunk/ppMerge/src/ppMergeMask.c	(revision 17430)
@@ -370,4 +370,16 @@
         }
 
+        psList *inChips = psListAlloc(NULL);
+        for (int i=0; i < numFiles; i++) {
+            pmFPAfile *file = pmFPAfileSelectSingle(config->files, "PPMERGE.INPUT", i); // Input file
+            pmChip *chip = pmFPAviewThisChip(view, file->fpa);
+            psListAdd(inChips, PS_LIST_TAIL, chip);
+        }
+        if (!pmConceptsAverageChips(outChip, inChips, true)) {
+            psError(PS_ERR_UNKNOWN, false, "Unable to average Chip concepts.");
+            psFree(inChips);
+            goto PPMERGE_MASK_ERROR;
+        }
+        psFree(inChips);
         if (!pmFPAfileIOChecks(config, view, PM_FPA_AFTER)) {
             goto PPMERGE_MASK_ERROR;