The debhelper compatibility version used by this package is marked as experimental by the debhelper developer. You should consider using a stable compatibility version instead.
The compatibility version can be set by specifying debhelper-compat (= 12) in your package's Build-Depends, by the legacy debian/compat file or even by setting and exporting DH_COMPAT in debian/rules. If it is not set in either place, debhelper defaults to the deprecated compatibility version 1.
Refer to the debhelper(7) manual page for details.