Index: /trunk/ppArith/src/ppArithArguments.c
===================================================================
--- /trunk/ppArith/src/ppArithArguments.c	(revision 15573)
+++ /trunk/ppArith/src/ppArithArguments.c	(revision 15574)
@@ -93,5 +93,5 @@
         goto ERROR;
     }
-    if ((isMask && file1->type != PM_FPA_FILE_MASK) || file1->type != PM_FPA_FILE_IMAGE) {
+    if ((isMask && file1->type != PM_FPA_FILE_MASK) || (!isMask && file1->type != PM_FPA_FILE_IMAGE)) {
         psError(PS_ERR_IO, true, "File rule %s is not of the expected type", inFilerule);
         goto ERROR;
@@ -107,5 +107,5 @@
             goto ERROR;
         }
-        if ((isMask && file2->type != PM_FPA_FILE_MASK) || file2->type != PM_FPA_FILE_IMAGE) {
+        if ((isMask && file2->type != PM_FPA_FILE_MASK) || (!isMask && file2->type != PM_FPA_FILE_IMAGE)) {
             psError(PS_ERR_IO, true, "File rule %s is not of the expected type", inFilerule);
             goto ERROR;
@@ -124,5 +124,5 @@
         goto ERROR;
     }
-    if ((isMask && output->type != PM_FPA_FILE_MASK) || output->type != PM_FPA_FILE_IMAGE) {
+    if ((isMask && output->type != PM_FPA_FILE_MASK) || (!isMask && output->type != PM_FPA_FILE_IMAGE)) {
         psError(PS_ERR_IO, true, "%s is not of the expected type", outFilerule);
         goto ERROR;