diff --git a/gnu/packages/ntp.scm b/gnu/packages/ntp.scm
index b3b4453945..d270f513dc 100644
--- a/gnu/packages/ntp.scm
+++ b/gnu/packages/ntp.scm
@@ -107,6 +107,8 @@ computers over a network.")
                (base32
                 "0fn12i4kzsi0zkr4qp3dp9bycmirnfapajqvdfx02zhr4hanj0kv"))))
     (build-system gnu-build-system)
+    (inputs
+     `(("libressl" ,libressl))) ; enable TLS time constraints. See ntpd.conf(5).
     (home-page "http://www.openntpd.org/")
     (synopsis "NTP client and server by the OpenBSD Project")
     (description "OpenNTPD is the OpenBSD Project's implementation of a client