-As of Babeltrace \btversion, \p packet_context_type \em must be a
-CTF IR structure field type object.
+If \p packet_header_type is \c NULL, then this function unsets the current
+packet header field type from \p trace_class, effectively making \p trace_class
+a trace without a packet header field type.
+
+As of Babeltrace \btversion, if \p packet_header_type is not \c NULL,
+\p packet_header_type \em must be a CTF IR structure field type object.