Index: myhdl/test/core/test_Cosimulation.py
--- myhdl/test/core/test_Cosimulation.py.orig
+++ myhdl/test/core/test_Cosimulation.py
@@ -36,7 +36,7 @@ random.seed(1)  # random, but deterministic
 
 MAXLINE = 4096
 
-exe = "python {0} ".format(os.path.abspath(__file__))
+exe = "${MODPY_BIN} {0} ".format(os.path.abspath(__file__))
 
 fromSignames = ['a', 'bb', 'ccc']
 fromSizes = [1, 11, 63]
