examples/public-inbox-httpd@.service | 5 +++++
 examples/public-inbox-nntpd@.service | 5 +++++
 examples/unsubscribe-psgi@.service   | 5 +++++

diff --git a/examples/public-inbox-httpd@.service b/examples/public-inbox-httpd@.service
index 56117ef09368405ac21683d62b33d14edfda0c63..e811da40497a402e88f1b58a614a8519e7980434 100644
--- a/examples/public-inbox-httpd@.service
+++ b/examples/public-inbox-httpd@.service
@@ -20,7 +20,12 @@ ExecStartPre = /bin/mkdir -p -m 1777 /tmp/.pub-inline
 ExecStart = /usr/local/bin/public-inbox-httpd \
 -1 /var/log/public-inbox/httpd.out.log
 StandardError = syslog
+
+# NonBlocking is REQUIRED to avoid a race condition if running
+# simultaneous services
+NonBlocking = true
 Sockets = public-inbox-httpd.socket
+
 KillSignal = SIGQUIT
 User = nobody
 Group = nogroup
diff --git a/examples/public-inbox-nntpd@.service b/examples/public-inbox-nntpd@.service
index 62202c2fa54e18a9f11da0fe0540f2c904a23864..a879841e6dacde6096c89d666547370cd150f4fe 100644
--- a/examples/public-inbox-nntpd@.service
+++ b/examples/public-inbox-nntpd@.service
@@ -20,7 +20,12 @@ ExecStartPre = /bin/mkdir -p -m 1777 /tmp/.pub-inline
 ExecStart = /usr/local/bin/public-inbox-nntpd \
 -1 /var/log/public-inbox/nntpd.out.log
 StandardError = syslog
+
+# NonBlocking is REQUIRED to avoid a race condition if running
+# simultaneous services
+NonBlocking = true
 Sockets = public-inbox-nntpd.socket
+
 KillSignal = SIGQUIT
 User = nobody
 Group = nogroup
diff --git a/examples/unsubscribe-psgi@.service b/examples/unsubscribe-psgi@.service
index acc29e8e64c648a448ac4433fd587a17da561f78..c8721fbe1d1bee5247ad721e656a5524dace2a72 100644
--- a/examples/unsubscribe-psgi@.service
+++ b/examples/unsubscribe-psgi@.service
@@ -12,7 +12,12 @@ [Service]
 # any PSGI server ought to work,
 # but public-inbox-httpd supports socket activation like unsubscribe.milter
 ExecStart = /usr/local/bin/public-inbox-httpd -W0 /etc/unsubscribe.psgi
+
+# NonBlocking is REQUIRED to avoid a race condition if running
+# simultaneous services
+NonBlocking = true
 Sockets = unsubscribe-psgi.socket
+
 # we need to modify the mlmmj spool
 User = mlmmj
 KillMode = process