diff --git a/artiq/coredevice/core.py b/artiq/coredevice/core.py
index 3e46260dc..146baadce 100644
--- a/artiq/coredevice/core.py
+++ b/artiq/coredevice/core.py
@@ -25,8 +25,8 @@ def rtio_get_destination_status(destination: int32) -> bool:
 def rtio_get_counter() -> int64:
     raise NotImplementedError("syscall not simulated")
 
-@syscall
-def test_exception_id_sync(id: TInt32) -> TNone:
+@extern
+def test_exception_id_sync(id: int32):
     raise NotImplementedError("syscall not simulated")
 
 artiq_builtins = {
diff --git a/artiq/test/coredevice/test_portability.py b/artiq/test/coredevice/test_portability.py
index 9ac52ab3f..8c7245559 100644
--- a/artiq/test/coredevice/test_portability.py
+++ b/artiq/test/coredevice/test_portability.py
@@ -1,3 +1,4 @@
+import unittest
 from operator import itemgetter
 
 from numpy import int32, int64