diff --git a/0001-tests-test-captive.sh-Increase-sleep-times.patch b/0001-tests-test-captive.sh-Increase-sleep-times.patch
index 11fea90..a1e223b 100644
--- a/0001-tests-test-captive.sh-Increase-sleep-times.patch
+++ b/0001-tests-test-captive.sh-Increase-sleep-times.patch
@@ -1,7 +1,7 @@
 From 740f6dee658ee6adb356d9600e2b51bb22dbce1e Mon Sep 17 00:00:00 2001
 From: "Richard W.M. Jones" <rjones@redhat.com>
 Date: Sat, 19 Oct 2019 18:31:24 +0100
-Subject: [PATCH 1/3] tests/test-captive.sh: Increase sleep times.
+Subject: [PATCH 1/4] tests/test-captive.sh: Increase sleep times.
 
 Short sleeps in this test make the test very prone to failure on slow
 or heavily loaded machines.
diff --git a/0002-tests-test-captive.sh-Remove-useless-sleep.patch b/0002-tests-test-captive.sh-Remove-useless-sleep.patch
index 6360027..e23195e 100644
--- a/0002-tests-test-captive.sh-Remove-useless-sleep.patch
+++ b/0002-tests-test-captive.sh-Remove-useless-sleep.patch
@@ -1,7 +1,7 @@
 From f4e7db5062dc59662ce05796f95f93017187f1d6 Mon Sep 17 00:00:00 2001
 From: "Richard W.M. Jones" <rjones@redhat.com>
 Date: Sat, 19 Oct 2019 18:52:47 +0100
-Subject: [PATCH 2/3] tests/test-captive.sh: Remove useless sleep.
+Subject: [PATCH 2/4] tests/test-captive.sh: Remove useless sleep.
 
 ---
  tests/test-captive.sh | 2 +-
diff --git a/0003-tests-test-socket-activation.c-Don-t-check-nbdkit-ex.patch b/0003-tests-test-socket-activation.c-Don-t-check-nbdkit-ex.patch
index b8a06a5..6230fdd 100644
--- a/0003-tests-test-socket-activation.c-Don-t-check-nbdkit-ex.patch
+++ b/0003-tests-test-socket-activation.c-Don-t-check-nbdkit-ex.patch
@@ -1,7 +1,7 @@
-From c3c6d81418c4dc23ac81dc2a6f5751a8c82667a3 Mon Sep 17 00:00:00 2001
+From b6cbb0edc94772ce063bc4a64d1940519fd87fa2 Mon Sep 17 00:00:00 2001
 From: "Richard W.M. Jones" <rjones@redhat.com>
 Date: Sat, 19 Oct 2019 19:11:22 +0100
-Subject: [PATCH 3/3] tests/test-socket-activation.c: Don't check nbdkit exit
+Subject: [PATCH 3/4] tests/test-socket-activation.c: Don't check nbdkit exit
  status.
 
 In this test we run nbdkit as a subprocess of the test.  The test
@@ -13,17 +13,19 @@ is not relevant so ignore the exit status.
 
 This makes the test more stable.
 ---
- tests/test-socket-activation.c | 23 +----------------------
- 1 file changed, 1 insertion(+), 22 deletions(-)
+ tests/test-socket-activation.c | 25 +------------------------
+ 1 file changed, 1 insertion(+), 24 deletions(-)
 
 diff --git a/tests/test-socket-activation.c b/tests/test-socket-activation.c
-index 2141d6d..64ec327 100644
+index 2141d6d..ec91114 100644
 --- a/tests/test-socket-activation.c
 +++ b/tests/test-socket-activation.c
-@@ -88,30 +88,9 @@ cleanup (void)
+@@ -86,32 +86,9 @@ static pid_t pid = 0;
+ static void
+ cleanup (void)
  {
-   int status;
- 
+-  int status;
+-
 -  if (pid > 0) {
 +  if (pid > 0)
      kill (pid, SIGTERM);
diff --git a/0004-tests-test-captive.sh-Better-test-for-pidfile.patch b/0004-tests-test-captive.sh-Better-test-for-pidfile.patch
new file mode 100644
index 0000000..27f7f6e
--- /dev/null
+++ b/0004-tests-test-captive.sh-Better-test-for-pidfile.patch
@@ -0,0 +1,39 @@
+From 57ae3c6098c35256ab1e3679f77ed28b5aad982a Mon Sep 17 00:00:00 2001
+From: "Richard W.M. Jones" <rjones@redhat.com>
+Date: Sat, 19 Oct 2019 19:42:40 +0100
+Subject: [PATCH 4/4] tests/test-captive.sh: Better test for pidfile.
+
+This test was still unstable on slower machines.  Improve the test for
+the pidfile to make it more stable.
+
+Fixes commit 740f6dee658ee6adb356d9600e2b51bb22dbce1e
+and commit 38165d0f8f5a4eb898d756a561811c2fe042fe4d.
+---
+ tests/test-captive.sh | 11 +++++++----
+ 1 file changed, 7 insertions(+), 4 deletions(-)
+
+diff --git a/tests/test-captive.sh b/tests/test-captive.sh
+index 22a90ca..82697a5 100755
+--- a/tests/test-captive.sh
++++ b/tests/test-captive.sh
+@@ -72,10 +72,13 @@ fi
+ # Check that nbdkit death from unhandled signal affects exit status
+ status=0
+ nbdkit -U - -P captive.pid example1 --run '
+-test ! -s captive.pid || sleep 5
+-if test ! -s captive.pid; then
+-  echo "no pidfile yet"
+-  exit 10
++for i in {1..60}; do
++    if test -s captive.pid; then break; fi
++    sleep 1
++done
++if ! test -s captive.pid; then
++    echo "$0: no pidfile yet"
++    exit 10
+ fi
+ kill -s ABRT $(cat captive.pid) || exit 10
+ sleep 5
+-- 
+2.23.0
+
diff --git a/nbdkit.spec b/nbdkit.spec
index 8b8f3bd..57b452d 100644
--- a/nbdkit.spec
+++ b/nbdkit.spec
@@ -41,11 +41,12 @@ Source1:        http://libguestfs.org/download/nbdkit/%{source_directory}/%{name
 Source2:       libguestfs.keyring
 %endif
 
-# Make tests/test-captive.sh stable.
+# Make tests/test-captive.sh and tests/test-socket-activation stable.
+# All upstream after nbdkit 1.15.5.
 Patch1:        0001-tests-test-captive.sh-Increase-sleep-times.patch
 Patch2:        0002-tests-test-captive.sh-Remove-useless-sleep.patch
-# Make tests/test-socket-activation stable.
 Patch3:        0003-tests-test-socket-activation.c-Don-t-check-nbdkit-ex.patch
+Patch4:        0004-tests-test-captive.sh-Better-test-for-pidfile.patch
 
 %if 0%{patches_touch_autotools}
 BuildRequires: autoconf, automake, libtool