diff --git a/_pytest/assertion/rewrite.py b/_pytest/assertion/rewrite.py
index 612dc8d35..43be4f696 100644
--- a/_pytest/assertion/rewrite.py
+++ b/_pytest/assertion/rewrite.py
@@ -109,7 +109,7 @@ class AssertionRewritingHook(object):
             mod.__file__ = co.co_filename
             # Normally, this attribute is 3.2+.
             mod.__cached__ = pyc
-            exec co in mod.__dict__
+            py.builtin.exec_(co, mod.__dict__)
         except:
             del sys.modules[name]
             raise