diff --git a/0001-tests-test-nozero.sh-Add-set-x.patch b/0001-tests-test-nozero.sh-Add-set-x.patch
index b4d4649..fb328e9 100644
--- a/0001-tests-test-nozero.sh-Add-set-x.patch
+++ b/0001-tests-test-nozero.sh-Add-set-x.patch
@@ -1,7 +1,7 @@
 From 5dc844e5b481b32915d38a9e5dd32bef3e698957 Mon Sep 17 00:00:00 2001
 From: "Richard W.M. Jones" <rjones@redhat.com>
 Date: Fri, 31 Jul 2020 08:51:37 +0100
-Subject: [PATCH] tests/test-nozero.sh: Add set -x.
+Subject: [PATCH 1/2] tests/test-nozero.sh: Add set -x.
 
 Used to track down a failure in this test which only happens in Koji.
 ---
diff --git a/0002-tests-test-nozero.sh-Create-test-file-as-single-exte.patch b/0002-tests-test-nozero.sh-Create-test-file-as-single-exte.patch
new file mode 100644
index 0000000..138c3ad
--- /dev/null
+++ b/0002-tests-test-nozero.sh-Create-test-file-as-single-exte.patch
@@ -0,0 +1,53 @@
+From 89a36b1fab8302ddc370695d386a28a03a74eae7 Mon Sep 17 00:00:00 2001
+From: "Richard W.M. Jones" <rjones@redhat.com>
+Date: Sat, 1 Aug 2020 08:46:53 +0100
+Subject: [PATCH 2/2] tests/test-nozero.sh: Create test file as single extent,
+ add debugging.
+
+Previously the test file was created by repeatedly appending, ie:
+
+$ rm file; for f in {0..1023}; do printf '%1024s' . >> file; done ; stat -c "%b %B" file
+3968 512
+
+This seems to create files which have more than one extent.  I have
+changed it to the simpler form:
+
+$ rm file; for f in {0..1023}; do printf '%1024s' .; done > file; stat -c "%b %B" file
+2048 512
+
+Also this commit adds debugging.
+---
+ tests/test-nozero.sh | 12 ++++++++++--
+ 1 file changed, 10 insertions(+), 2 deletions(-)
+
+diff --git a/tests/test-nozero.sh b/tests/test-nozero.sh
+index 9a815814..f1bb8a38 100755
+--- a/tests/test-nozero.sh
++++ b/tests/test-nozero.sh
+@@ -71,13 +71,21 @@ cleanup ()
+ }
+ cleanup_fn cleanup
+ 
+-# Prep images, and check that zero with trim results in a sparse image.
+-for f in {0..1023}; do printf '%1024s' . >> nozero1.img; done
++# Prep images.
++for f in {0..1023}; do printf '%1024s' . ; done > nozero1.img
+ cp nozero1.img nozero2.img
+ cp nozero1.img nozero3.img
+ cp nozero1.img nozero4.img
+ cp nozero1.img nozero5.img
+ cp nozero1.img nozero6.img
++
++# Debug number of blocks and block size in the images.
++for f in {1..6}; do
++    stat -c "%n: %b allocated blocks of size %B bytes, total size %s" \
++         nozero$f.img
++done
++
++# Check that zero with trim results in a sparse image.
+ requires nbdkit -U - --filter=log file logfile=nozero1.log nozero1.img \
+     --run 'nbdsh -u "$uri" -c "h.zero (1024*1024, 0)"'
+ if test "$(stat -c %b nozero1.img)" = "$(stat -c %b nozero2.img)"; then
+-- 
+2.28.0.rc2
+
diff --git a/nbdkit.spec b/nbdkit.spec
index b26855d..d802d70 100644
--- a/nbdkit.spec
+++ b/nbdkit.spec
@@ -45,7 +45,7 @@ ExclusiveArch:  x86_64
 
 Name:           nbdkit
 Version:        1.21.20
-Release:        4%{?dist}
+Release:        5%{?dist}
 Summary:        NBD server
 
 License:        BSD
@@ -60,6 +60,7 @@ Source2:       libguestfs.keyring
 
 # Upsream patch to try to track down test failure.
 Patch1:        0001-tests-test-nozero.sh-Add-set-x.patch
+Patch2:        0002-tests-test-nozero.sh-Create-test-file-as-single-exte.patch
 
 %if 0%{patches_touch_autotools}
 BuildRequires: autoconf, automake, libtool
@@ -667,10 +668,6 @@ autoreconf -i
 
 
 %build
-# Disable LTO, it's unreliable.  See for example:
-# https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/thread/ULGH5JYL7MHKDKTINJLOEN2QG6LOHWH7/
-%define _lto_cflags %{nil}
-
 # Golang bindings are not enabled in the Fedora build since they don't
 # need to be.  Most people would use them by copying the upstream
 # package into their vendor/ directory.
@@ -1075,9 +1072,8 @@ export LIBGUESTFS_TRACE=1
 
 
 %changelog
-* Fri Jul 31 2020 Richard W.M. Jones <rjones@redhat.com> - 1.21.20-4
-- Add upstream patch to try to track down test failure in Koji.
-- Disable LTO.
+* Sat Aug  1 2020 Richard W.M. Jones <rjones@redhat.com> - 1.21.20-5
+- Add upstream patches to try to track down test failure in Koji.
 
 * Tue Jul 28 2020 Fedora Release Engineering <releng@fedoraproject.org> - 1.21.20-2
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_33_Mass_Rebuild