diff --git a/acme/challenges.py b/acme/challenges.py
index 36c29d6c6..26f71a2e3 100644
--- a/acme/challenges.py
+++ b/acme/challenges.py
@@ -46,6 +46,7 @@ class SimpleHTTP(DVChallenge):
     """ACME "simpleHttp" challenge."""
     typ = "simpleHttp"
     token = jose.Field("token")
+    tls = jose.Field("tls", default=True, omitempty=True)
 
 
 @ChallengeResponse.register