diff --git a/docs/libssh2_knownhost_add.3 b/docs/libssh2_knownhost_add.3
index a416a3f1..c9855beb 100644
--- a/docs/libssh2_knownhost_add.3
+++ b/docs/libssh2_knownhost_add.3
@@ -21,7 +21,7 @@ of the host or the full name.
 
 \fIsalt\P is a pointer to the salt used for the host hashing, if the host is
 provided hashed. If the host is provided in plain text, salt has no meaning.
-The salt has to be provided base64 encoded.
+The salt has to be provided base64 encoded with a trailing zero byte.
 
 \fIkey\fP is a pointer to the key for the given host.