diff -Nru libgnatcoll-19/debian/changelog libgnatcoll-19/debian/changelog
--- libgnatcoll-19/debian/changelog	2019-12-30 22:32:05.000000000 +0000
+++ libgnatcoll-19/debian/changelog	2020-02-25 14:28:56.000000000 +0000
@@ -1,3 +1,12 @@
+libgnatcoll (19-4) unstable; urgency=medium
+
+  * Reupload to unstable for gnat-9 transition.
+  * Use debhelper 12 dh-sequenc syntax.
+  * Wrap and sort build dependencies.
+  * Standards-Version: 4.5.0.
+
+ -- Nicolas Boulenguez <nicolas@debian.org>  Tue, 25 Feb 2020 15:28:56 +0100
+
 libgnatcoll (19-3) experimental; urgency=medium
 
   * Use dh-sequence-* syntax for dh-ada-library.
diff -Nru libgnatcoll-19/debian/control libgnatcoll-19/debian/control
--- libgnatcoll-19/debian/control	2019-12-30 22:23:41.000000000 +0000
+++ libgnatcoll-19/debian/control	2020-02-25 14:28:14.000000000 +0000
@@ -12,17 +12,17 @@
  libgnatprj7-dev,
 # Implicit libc6-dev provides: iconv, syslog.
 Build-Depends-Indep:
- python3-sphinx,
+ dh-sequence-sphinxdoc,
+# Sphinx >= 1.6 uses the latexmk driver:
  latexmk,
-# Sphinx >= 1.6 uses the latexmk driver.
+ python3-sphinx,
+ sphinx-common,
  texlive-fonts-recommended,
+ texlive-latex-extra,
 # sphinx-doc requires iftex.sty:
  texlive-plain-generic,
- texlive-latex-extra
-# dh_sphinxdoc
- ,sphinx-common
 Homepage: https://www.adacore.com/community
-Standards-Version: 4.4.1
+Standards-Version: 4.5.0
 Rules-Requires-Root: no
 Vcs-Browser: https://salsa.debian.org/debian/libgnatcoll
 Vcs-Git: https://salsa.debian.org/debian/libgnatcoll.git
diff -Nru libgnatcoll-19/debian/rules libgnatcoll-19/debian/rules
--- libgnatcoll-19/debian/rules	2019-12-30 22:32:05.000000000 +0000
+++ libgnatcoll-19/debian/rules	2020-01-12 18:17:06.000000000 +0000
@@ -58,10 +58,8 @@
 # Ignore upstream install target.
 .PHONY: override_dh_auto_install
 
-# Mimic 'dh --with sphinxdoc', but without adding sphinx-common to
-# Build-Depends for arch-only builds.
 # Avoid a warning about doc-main-package.
-.PHONY: override_dh_installdocs-indep
-override_dh_installdocs-indep:
+.PHONY: override_dh_installdocs
+override_dh_installdocs:
 	dh_installdocs --package=libgnatcoll-doc --doc-main-package=libgnatcoll-doc
-	dh_sphinxdoc
+	dh_installdocs --remaining-packages