diff -r 000000000000 -r 6474c204b198 dom/bindings/parser/tests/test_nullable_void.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/bindings/parser/tests/test_nullable_void.py	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,14 @@
+def WebIDLTest(parser, harness):
+    threw = False
+    try:
+        parser.parse("""
+            interface NullableVoid {
+              void? foo();
+            };
+        """)
+
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown.")