in_reply_to = *i;
if (i != message->doc.termlist_end () &&
- strncmp ((*i).c_str (), prefix, prefix_len))
+ strncmp ((*i).c_str (), prefix, prefix_len) == 0)
{
INTERNAL_ERROR ("Message %s has duplicate In-Reply-To IDs: %s and %s\n",
notmuch_message_get_message_id (message),