diff --git a/testing/test_assertrewrite.py b/testing/test_assertrewrite.py
index df6620d11..1d1f04f97 100644
--- a/testing/test_assertrewrite.py
+++ b/testing/test_assertrewrite.py
@@ -29,7 +29,7 @@ def getmsg(f, extra_ns=None, must_pass=False):
     ns = {}
     if extra_ns is not None:
         ns.update(extra_ns)
-    exec code in ns
+    py.builtin.exec_(code, ns)
     func = ns[f.__name__]
     try:
         func()