diff --git a/myhdl/test/core/test_Cosimulation.py b/myhdl/test/core/test_Cosimulation.py
index bd47e3d5..97896a89 100644
--- a/myhdl/test/core/test_Cosimulation.py
+++ b/myhdl/test/core/test_Cosimulation.py
@@ -245,7 +245,7 @@ class CosimulationTest(TestCase):
         cosim._getMode = 1
         cosim._get()
         for n in toSignames:
-            self.assertEqual(toSigs[n].next, None)
+            self.assertEqual(toSigs[n].next, 0)
         
 
     def cosimToSignalVals(self):