Index: /trunk/psLib/src/imageops/psImageBackground.c
===================================================================
--- /trunk/psLib/src/imageops/psImageBackground.c	(revision 9974)
+++ /trunk/psLib/src/imageops/psImageBackground.c	(revision 9975)
@@ -26,4 +26,5 @@
     PS_ASSERT_FLOAT_LESS_THAN_OR_EQUAL(fmax, 1.0, NULL);
     PS_ASSERT_INT_POSITIVE(nMax, NULL);
+    PS_ASSERT_PTR_NON_NULL(rng, NULL);
 
     // Size of image