In this case error out when no query is supplied. There seems to be an infinite-loop casued by i think notmuch_query_search_threads having an exception: A Xapian exception occurred: Syntax: <expression> AND <expression> A Xapian exception occurred: Syntax: <expression> AND <expression> A Xapian exception occurred: Syntax: <expression> AND <expression> A Xapian exception occurred: Syntax: <expression> AND <expression> A Xapian exception occurred: Syntax: <expression> AND <expression> A Xapian exception occurred: Syntax: <expression> AND <expression> A Xapian exception occurred: Syntax: <expression> AND <expression> A Xapian exception occurred: Syntax: <expression> AND <expression> A Xapian exception occurred: Syntax: <expression> AND <expression> A Xapian exception occurred: Syntax: <expression> AND <expression> A Xapian exception occurred: Syntax: <expression> AND <expression> A Xapian exception occurred: Syntax: <expression> AND <expression> A Xapian exception occurred: Syntax: <expression> AND <expression> A Xapian exception occurred: Syntax: <expression> AND <expression> A Xapian exception occurred: Syntax: <expression> AND <expression> I'll look into that bug specifically a bit later. It might be better to do a usage instead of just throwing an error here? alex