diff -Nru squid3-3.5.12/debian/changelog squid3-3.5.12/debian/changelog
--- squid3-3.5.12/debian/changelog	2016-03-30 00:34:07.000000000 +0000
+++ squid3-3.5.12/debian/changelog	2016-03-30 02:46:17.000000000 +0000
@@ -1,3 +1,10 @@
+squid3 (3.5.12-1ubuntu3) xenial; urgency=medium
+
+  * Revert last postinst change as it's buggy.
+  * Remove /etc/init.d/squid3 from preinst on upgrade.
+
+ -- Stéphane Graber <stgraber@ubuntu.com>  Tue, 29 Mar 2016 22:46:16 -0400
+
 squid3 (3.5.12-1ubuntu2) xenial; urgency=medium
 
   * debian/squid.postinst: Fix dist-upgrade of squid by detecting service
diff -Nru squid3-3.5.12/debian/squid3.postinst squid3-3.5.12/debian/squid3.postinst
--- squid3-3.5.12/debian/squid3.postinst	2016-02-24 15:25:37.000000000 +0000
+++ squid3-3.5.12/debian/squid3.postinst	2016-03-30 03:00:34.000000000 +0000
@@ -44,6 +44,10 @@
 dpkg-maintscript-helper rm_conffile \
 	/etc/init/squid3.conf 3.5.10-1ubuntu1~ squid3 -- "$@"
 
+# Ubuntu: remove old init script (no longer shipped)
+dpkg-maintscript-helper rm_conffile \
+	/etc/init.d/squid3 3.5.12-1ubuntu3~ squid3 -- "$@"
+
 # Ubuntu: rename Apparmor profile to follow squid3->squid rename
 dpkg-maintscript-helper mv_conffile \
 	/etc/apparmor.d/usr.sbin.squid3 /etc/apparmor.d/usr.sbin.squid 3.5.10-1ubuntu1~ squid3 -- "$@"
diff -Nru squid3-3.5.12/debian/squid3.postrm squid3-3.5.12/debian/squid3.postrm
--- squid3-3.5.12/debian/squid3.postrm	2016-02-24 15:25:37.000000000 +0000
+++ squid3-3.5.12/debian/squid3.postrm	2016-03-30 03:01:24.000000000 +0000
@@ -37,6 +37,10 @@
 dpkg-maintscript-helper rm_conffile \
 	/etc/init/squid3.conf 3.5.10-1ubuntu1~ squid3 -- "$@"
 
+# Ubuntu: remove old init script (no longer shipped)
+dpkg-maintscript-helper rm_conffile \
+	/etc/init.d/squid3 3.5.12-1ubuntu3~ squid3 -- "$@"
+
 # Ubuntu: rename Apparmor profile to follow squid3->squid rename
 dpkg-maintscript-helper mv_conffile \
 	/etc/apparmor.d/usr.sbin.squid3 /etc/apparmor.d/usr.sbin.squid 3.5.10-1ubuntu1~ squid3 -- "$@"
diff -Nru squid3-3.5.12/debian/squid3.preinst squid3-3.5.12/debian/squid3.preinst
--- squid3-3.5.12/debian/squid3.preinst	2016-02-24 15:25:37.000000000 +0000
+++ squid3-3.5.12/debian/squid3.preinst	2016-03-30 03:01:09.000000000 +0000
@@ -41,6 +41,10 @@
 dpkg-maintscript-helper rm_conffile \
 	/etc/init/squid3.conf 3.5.10-1ubuntu1~ squid3 -- "$@"
 
+# Ubuntu: remove old init script (no longer shipped)
+dpkg-maintscript-helper rm_conffile \
+	/etc/init.d/squid3 3.5.12-1ubuntu3~ squid3 -- "$@"
+
 # Ubuntu: rename Apparmor profile to follow squid3->squid rename
 dpkg-maintscript-helper mv_conffile \
 	/etc/apparmor.d/usr.sbin.squid3 /etc/apparmor.d/usr.sbin.squid 3.5.10-1ubuntu1~ squid3 -- "$@"
diff -Nru squid3-3.5.12/debian/squid.postinst squid3-3.5.12/debian/squid.postinst
--- squid3-3.5.12/debian/squid.postinst	2016-03-30 00:34:07.000000000 +0000
+++ squid3-3.5.12/debian/squid.postinst	2016-03-30 03:01:17.000000000 +0000
@@ -37,6 +37,10 @@
 dpkg-maintscript-helper rm_conffile \
 	/etc/init/squid3.conf 3.5.10-1ubuntu1~ squid3 -- "$@"
 
+# Ubuntu: remove old init script (no longer shipped)
+dpkg-maintscript-helper rm_conffile \
+	/etc/init.d/squid3 3.5.12-1ubuntu3~ squid3 -- "$@"
+
 # Ubuntu: rename Apparmor profile to follow squid3->squid rename
 dpkg-maintscript-helper mv_conffile \
 	/etc/apparmor.d/usr.sbin.squid3 /etc/apparmor.d/usr.sbin.squid 3.5.10-1ubuntu1~ squid3 -- "$@"
@@ -109,16 +113,8 @@
 update-rc.d squid defaults 30 >/dev/null
 
 if test -d /etc/squid3 && dpkg --compare-versions "$2" lt '3.5'; then
-	#
-	# handle the case where we have /etc/squid3 but the init script is
-	# named squid.
-	#
-	service=squid3
-	if ! test -e /etc/init.d/$service ; then
-		service=squid
-	fi
-	invoke-rc.d $service stop
-	invoke-rc.d $service start
+	invoke-rc.d squid3 stop
+	invoke-rc.d squid start
 else
 	invoke-rc.d squid restart
 fi
diff -Nru squid3-3.5.12/debian/squid.postrm squid3-3.5.12/debian/squid.postrm
--- squid3-3.5.12/debian/squid.postrm	2016-02-24 15:25:49.000000000 +0000
+++ squid3-3.5.12/debian/squid.postrm	2016-03-30 03:00:52.000000000 +0000
@@ -37,6 +37,10 @@
 dpkg-maintscript-helper rm_conffile \
 	/etc/init/squid3.conf 3.5.10-1ubuntu1~ squid3 -- "$@"
 
+# Ubuntu: remove old init script (no longer shipped)
+dpkg-maintscript-helper rm_conffile \
+	/etc/init.d/squid3 3.5.12-1ubuntu3~ squid3 -- "$@"
+
 # Ubuntu: rename Apparmor profile to follow squid3->squid rename
 dpkg-maintscript-helper mv_conffile \
 	/etc/apparmor.d/usr.sbin.squid3 /etc/apparmor.d/usr.sbin.squid 3.5.10-1ubuntu1~ squid3 -- "$@"
diff -Nru squid3-3.5.12/debian/squid.preinst squid3-3.5.12/debian/squid.preinst
--- squid3-3.5.12/debian/squid.preinst	2016-02-24 15:26:06.000000000 +0000
+++ squid3-3.5.12/debian/squid.preinst	2016-03-30 02:45:56.000000000 +0000
@@ -41,6 +41,10 @@
 dpkg-maintscript-helper rm_conffile \
 	/etc/init/squid3.conf 3.5.10-1ubuntu1~ squid3 -- "$@"
 
+# Ubuntu: remove old init script (no longer shipped)
+dpkg-maintscript-helper rm_conffile \
+	/etc/init.d/squid3 3.5.12-1ubuntu3~ squid3 -- "$@"
+
 # Ubuntu: rename Apparmor profile to follow squid3->squid rename
 dpkg-maintscript-helper mv_conffile \
 	/etc/apparmor.d/usr.sbin.squid3 /etc/apparmor.d/usr.sbin.squid 3.5.10-1ubuntu1~ squid3 -- "$@"