Index: src/inter_call.c
===================================================================
--- src/inter_call.c	(revision 20860)
+++ src/inter_call.c	(working copy)
@@ -1463,6 +1463,9 @@
         arg_ret_cnt[seen_arrow]++;
         max_regs[REGNO_PMC]++;
     }
+    else {
+        real_exception(interp, NULL, 1, "Passed a NULL pmc");
+    }
 
     /* first loop through signature to get sizing info */
     for (x = signature; *x != '\0'; x++) {