diff --git a/uninit.patch b/uninit.patch
new file mode 100644
index 0000000..85053ce
--- /dev/null
+++ b/uninit.patch
@@ -0,0 +1,29 @@
+From: Jan Engelhardt <jengelh@inai.de>
+Date: 2019-08-26 14:13:15.685236019 +0200
+
+varnish screwing itself by use of -Werror.
+
+[   34s] vtc_haproxy.c: In function 'haproxy_start':
+[   34s] vtc_haproxy.c:442:10: error: 'pid' may be used uninitialized in this function [-Werror=maybe-uninitialized]
+[   34s]   442 |   h->pid = pid;
+[   34s]       |          ^
+[   34s] vtc_haproxy.c:413:8: note: 'pid' was declared here
+[   34s]   413 |  pid_t pid;
+
+---
+ bin/varnishtest/vtc_haproxy.c |    2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+Index: varnish-6.2.0/bin/varnishtest/vtc_haproxy.c
+===================================================================
+--- varnish-6.2.0.orig/bin/varnishtest/vtc_haproxy.c
++++ varnish-6.2.0/bin/varnishtest/vtc_haproxy.c
+@@ -410,7 +410,7 @@ haproxy_wait_pidfile(struct haproxy *h)
+ 	char buf_err[1024] = {0};
+ 	int usleep_time = 1000;
+ 	double t0;
+-	pid_t pid;
++	pid_t pid = 0;
+ 
+ 	vtc_log(h->vl, 3, "wait-pid-file");
+ 	for (t0 = VTIM_mono(); VTIM_mono() - t0 < 3;) {
diff --git a/varnish.changes b/varnish.changes
index 5b36ff1..9feb786 100644
--- a/varnish.changes
+++ b/varnish.changes
@@ -1,3 +1,8 @@
+-------------------------------------------------------------------
+Mon Aug 26 10:52:05 UTC 2019 - Jan Engelhardt <jengelh@inai.de>
+
+- Add uninit.patch.
+
 -------------------------------------------------------------------
 Wed Mar 27 10:01:08 UTC 2019 - Samu Voutilainen <smar@smar.fi>
 
diff --git a/varnish.spec b/varnish.spec
index 6f5ae9c..3bca521 100644
--- a/varnish.spec
+++ b/varnish.spec
@@ -40,6 +40,7 @@ Source5:        varnish.logrotate
 Source7:        varnish.service
 Source8:        varnishlog.service
 Patch1:         varnish-5.1.2-add-fallthrough-comments.patch
+Patch2:         uninit.patch
 BuildRequires:  python3-docutils
 BuildRequires:  python3-Sphinx
 BuildRequires:  libxslt
@@ -98,7 +99,7 @@ This package holds the development files for varnish.
 %autosetup -p1
 
 %build
-export CFLAGS="%optflags -fstack-protector -Wno-error=clobbered"
+export CFLAGS="%optflags -fstack-protector -Wno-error=clobbered -Werror=maybe-uninitialized"
 %ifarch %ix86
 export CFLAGS="$CFLAGS -ffloat-store -fexcess-precision=standard"
 %endif