diff -Nru plplot-5.15.0+dfsg/debian/changelog plplot-5.15.0+dfsg/debian/changelog
--- plplot-5.15.0+dfsg/debian/changelog	2020-12-14 17:45:18.000000000 +0000
+++ plplot-5.15.0+dfsg/debian/changelog	2020-12-16 09:20:37.000000000 +0000
@@ -1,3 +1,10 @@
+plplot (5.15.0+dfsg-19ubuntu1) hirsute; urgency=low
+
+  * Merge from Debian unstable. Remaining changes:
+    - Lower optimization level to -O1 on s390x to fix test failures.
+
+ -- Gianfranco Costamagna <locutusofborg@debian.org>  Wed, 16 Dec 2020 10:20:37 +0100
+
 plplot (5.15.0+dfsg-19) unstable; urgency=medium
 
   * d/rules: Really generate the d/plplotada.gpr file
@@ -40,6 +47,19 @@
 
  -- Rafael Laboissière <rafael@debian.org>  Sun, 15 Nov 2020 06:46:20 -0300
 
+plplot (5.15.0+dfsg-16ubuntu2) hirsute; urgency=medium
+
+  * No-change rebuild to build with python3.9 as default.
+
+ -- Matthias Klose <doko@ubuntu.com>  Thu, 19 Nov 2020 18:37:40 +0100
+
+plplot (5.15.0+dfsg-16ubuntu1) hirsute; urgency=low
+
+  * Merge from Debian unstable. Remaining changes:
+    - Lower optimization level to -O1 on s390x to fix test failures.
+
+ -- Gianfranco Costamagna <locutusofborg@debian.org>  Mon, 09 Nov 2020 11:51:55 +0100
+
 plplot (5.15.0+dfsg-16) unstable; urgency=medium
 
   * d/pbuild-against-qt-5.15.patch: New patch
@@ -57,6 +77,13 @@
 
  -- Rafael Laboissière <rafael@debian.org>  Tue, 06 Oct 2020 02:13:58 -0300
 
+plplot (5.15.0+dfsg-14ubuntu1) groovy; urgency=low
+
+  * Merge from Debian unstable.  Remaining changes:
+    - Lower optimization level to -O1 on s390x to fix test failures.
+
+ -- Gianfranco Costamagna <locutusofborg@debian.org>  Thu, 03 Sep 2020 14:05:18 +0200
+
 plplot (5.15.0+dfsg-14) unstable; urgency=medium
 
   * d/rules: Force a lower optimization level on ppc64el.
@@ -65,6 +92,13 @@
 
  -- Rafael Laboissière <rafael@debian.org>  Wed, 02 Sep 2020 06:11:39 -0300
 
+plplot (5.15.0+dfsg-13ubuntu3) groovy; urgency=medium
+
+  * Lower optimization level to -O2 on ppc64el and to -O1 on s390x to fix test
+    failures.
+
+ -- Gianfranco Costamagna <locutusofborg@debian.org>  Mon, 24 Aug 2020 14:44:15 +0200
+
 plplot (5.15.0+dfsg-13) unstable; urgency=medium
 
   * d/control: Bump debhelper compatibility level to 13
diff -Nru plplot-5.15.0+dfsg/debian/rules plplot-5.15.0+dfsg/debian/rules
--- plplot-5.15.0+dfsg/debian/rules	2020-12-14 16:06:32.000000000 +0000
+++ plplot-5.15.0+dfsg/debian/rules	2020-12-14 22:09:00.000000000 +0000
@@ -8,7 +8,11 @@
 ifeq ($(DEB_HOST_ARCH), ppc64el)
 DEB_CFLAGS_MAINT_APPEND       := -fvisibility=hidden -O2
 else
-DEB_CFLAGS_MAINT_APPEND       := -fvisibility=hidden
+ifeq ($(DEB_HOST_ARCH), s390x)
+ DEB_CFLAGS_MAINT_APPEND       := -fvisibility=hidden -O1
+else
+ DEB_CFLAGS_MAINT_APPEND       := -fvisibility=hidden
+endif
 endif
 
 DEB_FFLAGS_MAINT_APPEND       := -fvisibility=hidden