Index: src/inter_call.c
===================================================================
--- src/inter_call.c	(revision 11276)
+++ src/inter_call.c	(working copy)
@@ -728,6 +728,7 @@
                 enum_class_ResizablePMCArray));
     CTX_REG_PMC(st->dest.ctx, idx) = st->dest.slurp;
     st->dest.mode |= CALL_STATE_SLURP;
+    st->dest.mode &= ~CALL_STATE_OPT;
 }
 
 static void 
@@ -916,8 +917,9 @@
                 break;
 
             default:
-                internal_exception(1, "Unhandled process_args state 0x%x",
-                        state);
+                real_exception(interpreter, NULL, 0,
+                               "Unhandled process_args state 0x%x",
+                               state);
         }
     } while (1);
 }
Index: t/op/calling.t
===================================================================
--- t/op/calling.t	(revision 11276)
+++ t/op/calling.t	(working copy)
@@ -1714,6 +1714,38 @@
 ok
 OUTPUT
 
+pir_output_is(<<'CODE', <<'OUTPUT', ":optional followed by :slurpy (empty)");
+.sub main :main
+	_write_thing(3)
+.end
+.sub _write_thing
+	.param pmc arg1 :optional
+	.param pmc rest_arg :slurpy
+	print arg1
+	print ' '
+	print rest_arg
+	print "\n"
+.end
+CODE
+3 0
+OUTPUT
+
+pir_output_is(<<'CODE', <<'OUTPUT', ":optional followed by :slurpy (used)");
+.sub main :main
+	_write_thing(3, 4, 5)
+.end
+.sub _write_thing
+	.param pmc arg1 :optional
+	.param pmc rest_arg :slurpy
+	print arg1
+	print ' '
+	print rest_arg
+	print "\n"
+.end
+CODE
+3 2
+OUTPUT
+
 ## remember to change the number of tests :-)
-BEGIN { plan tests => 64; }
+BEGIN { plan tests => 66; }