diff --git a/Lib/email/contentmanager.py b/Lib/email/contentmanager.py
index b91fb0e..3cf62dc 100644
--- a/Lib/email/contentmanager.py
+++ b/Lib/email/contentmanager.py
@@ -238,9 +238,7 @@ def set_bytes_content(msg, data, maintype, subtype, cte='base64',
         data = binascii.b2a_qp(data, istext=False, header=False, quotetabs=True)
         data = data.decode('ascii')
     elif cte == '7bit':
-        # Make sure it really is only ASCII.  The early warning here seems
-        # worth the overhead...if you care write your own content manager :).
-        data.encode('ascii')
+        data = data.decode('ascii')
     elif cte in ('8bit', 'binary'):
         data = data.decode('ascii', 'surrogateescape')
     msg.set_payload(data)