diff --git a/man/rules/meson.build b/man/rules/meson.build
index 84f0442b1e2e3..2096222c50da3 100644
--- a/man/rules/meson.build
+++ b/man/rules/meson.build
@@ -718,7 +718,7 @@ manpages = [
  ['sd_machine_get_class', '3', ['sd_machine_get_ifindices'], ''],
  ['sd_notify',
   '3',
-  ['sd_notifyf', 'sd_pid_notify', 'sd_pid_notify_with_fds', 'sd_pid_notifyf'],
+  ['sd_notifyf', 'sd_pid_notify', 'sd_pid_notify_with_fds', 'sd_pid_notifyf', 'sd_notify_barrier'],
   ''],
  ['sd_path_lookup', '3', ['sd_path_lookup_strv'], ''],
  ['sd_pid_get_owner_uid',
diff --git a/man/sd_notify.xml b/man/sd_notify.xml
index 3046ca88ee728..dcc8fce69531b 100644
--- a/man/sd_notify.xml
+++ b/man/sd_notify.xml
@@ -22,6 +22,7 @@
     <refname>sd_pid_notify</refname>
     <refname>sd_pid_notifyf</refname>
     <refname>sd_pid_notify_with_fds</refname>
+    <refname>sd_notify_barrier</refname>
     <refpurpose>Notify service manager about start-up completion and other service status changes</refpurpose>
   </refnamediv>
 
@@ -65,6 +66,12 @@
         <paramdef>const int *<parameter>fds</parameter></paramdef>
         <paramdef>unsigned <parameter>n_fds</parameter></paramdef>
       </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_notify_barrier</function></funcdef>
+        <paramdef>int <parameter>unset_environment</parameter></paramdef>
+        <paramdef>uint64_t <parameter>timeout</parameter></paramdef>
+      </funcprototype>
     </funcsynopsis>
   </refsynopsisdiv>
 
@@ -251,6 +258,17 @@
         submitted name does not follow these restrictions, it is ignored.</para></listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term>BARRIER=1</term>
+
+        <listitem><para>Tells the service manager that the client is explicitly requesting synchronization by means of
+        closing the file descriptor sent with this command. The service manager gurantees that the processing of a <varname>
+        BARRIER=1</varname> command will only happen after all previous notification messages sent before this command
+        have been processed. Hence, this command accompanied with a single file descriptor can be used to synchronize
+        against reception of all previous status messages. Note that this command cannot be mixed with other notifications,
+        and has to be sent in a separate message to the service manager, otherwise all assignments will be ignored. Note that
+        sending 0 or more than 1 file descriptor with this command is a violation of the protocol.</para></listitem>
+      </varlistentry>
     </variablelist>
 
     <para>It is recommended to prefix variable names that are not
@@ -272,6 +290,13 @@
     attribute the message to the unit, and thus will ignore it, even if
     <varname>NotifyAccess=</varname><option>all</option> is set for it.</para>
 
+    <para>Hence, to eliminate all race conditions involving lookup of the client's unit and attribution of notifications
+    to units correctly, <function>sd_notify_barrier()</function> may be used. This call acts as a synchronization point
+    and ensures all notifications sent before this call have been picked up by the service manager when it returns
+    successfully. Use of <function>sd_notify_barrier()</function> is needed for clients which are not invoked by the
+    service manager, otherwise this synchronization mechanism is unnecessary for attribution of notifications to the
+    unit.</para>
+
     <para><function>sd_notifyf()</function> is similar to
     <function>sd_notify()</function> but takes a
     <function>printf()</function>-like format string plus
@@ -302,6 +327,14 @@
     to the service manager on messages that do not expect them (i.e.
     without <literal>FDSTORE=1</literal>) they are immediately closed
     on reception.</para>
+
+    <para><function>sd_notify_barrier()</function> allows the caller to
+    synchronize against reception of previously sent notification messages
+    and uses the <literal>BARRIER=1</literal> command. It takes a relative
+    <varname>timeout</varname> value in microseconds which is passed to
+    <citerefentry><refentrytitle>ppoll</refentrytitle><manvolnum>2</manvolnum>
+    </citerefentry>. A value of UINT64_MAX is interpreted as infinite timeout.
+    </para>
   </refsect1>
 
   <refsect1>
@@ -392,6 +425,22 @@
 
       <programlisting>sd_pid_notify_with_fds(0, 0, "FDSTORE=1\nFDNAME=foobar", &amp;fd, 1);</programlisting>
     </example>
+
+    <example>
+      <title>Eliminating race conditions</title>
+
+      <para>When the client sending the notifications is not spawned
+      by the service manager, it may exit too quickly and the service
+      manager may fail to attribute them correctly to the unit. To
+      prevent such races, use <function>sd_notify_barrier()</function>
+      to synchronize against reception of all notifications sent before
+      this call is made.</para>
+
+      <programlisting>sd_notify(0, "READY=1");
+      /* set timeout to 5 seconds */
+      sd_notify_barrier(0, 5 * 1000000);
+      </programlisting>
+    </example>
   </refsect1>
 
   <refsect1>
diff --git a/src/core/manager.c b/src/core/manager.c
index 43b8a02e488ab..501e37339b82f 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -2284,6 +2284,20 @@ static int manager_dispatch_cgroups_agent_fd(sd_event_source *source, int fd, ui
         return 0;
 }
 
+static bool manager_process_barrier_fd(const char *buf, FDSet *fds) {
+        assert(buf);
+
+        /* nothing else must be sent when using BARRIER=1 */
+        if (STR_IN_SET(buf, "BARRIER=1", "BARRIER=1\n")) {
+                if (fdset_size(fds) != 1)
+                        log_warning("Got incorrect number of fds with BARRIER=1, closing them.");
+                return true;
+        } else if (startswith(buf, "BARRIER=1\n") || strstr(buf, "\nBARRIER=1\n") || endswith(buf, "\nBARRIER=1"))
+                log_warning("Extra notification messages sent with BARRIER=1, ignoring everything.");
+
+        return false;
+}
+
 static void manager_invoke_notify_message(
                 Manager *m,
                 Unit *u,
@@ -2417,6 +2431,10 @@ static int manager_dispatch_notify_fd(sd_event_source *source, int fd, uint32_t
         /* Make sure it's NUL-terminated. */
         buf[n] = 0;
 
+        /* possibly a barrier fd, let's see */
+        if (manager_process_barrier_fd(buf, fds))
+                return 0;
+
         /* Increase the generation counter used for filtering out duplicate unit invocations. */
         m->notifygen++;
 
diff --git a/src/libsystemd/sd-daemon/sd-daemon.c b/src/libsystemd/sd-daemon/sd-daemon.c
index 4cd71cb2d3a02..587a1f2595bfe 100644
--- a/src/libsystemd/sd-daemon/sd-daemon.c
+++ b/src/libsystemd/sd-daemon/sd-daemon.c
@@ -4,6 +4,7 @@
 #include <limits.h>
 #include <mqueue.h>
 #include <netinet/in.h>
+#include <poll.h>
 #include <stdarg.h>
 #include <stddef.h>
 #include <stdio.h>
@@ -23,6 +24,7 @@
 #include "process-util.h"
 #include "socket-util.h"
 #include "strv.h"
+#include "time-util.h"
 #include "util.h"
 
 #define SNDBUF_SIZE (8*1024*1024)
@@ -551,6 +553,34 @@ _public_ int sd_pid_notify_with_fds(
         return r;
 }
 
+_public_ int sd_notify_barrier(int unset_environment, uint64_t timeout) {
+        _cleanup_close_pair_ int pipe_fd[2] = { -1, -1 };
+        struct timespec ts;
+        int r;
+
+        if (pipe2(pipe_fd, O_CLOEXEC) < 0)
+                return -errno;
+
+        r = sd_pid_notify_with_fds(0, unset_environment, "BARRIER=1", &pipe_fd[1], 1);
+        if (r <= 0)
+                return r;
+
+        pipe_fd[1] = safe_close(pipe_fd[1]);
+
+        struct pollfd pfd = {
+                .fd = pipe_fd[0],
+                /* POLLHUP is implicit */
+                .events = 0,
+        };
+        r = ppoll(&pfd, 1, timeout == UINT64_MAX ? NULL : timespec_store(&ts, timeout), NULL);
+        if (r < 0)
+                return -errno;
+        if (r == 0)
+                return -ETIMEDOUT;
+
+        return 1;
+}
+
 _public_ int sd_pid_notify(pid_t pid, int unset_environment, const char *state) {
         return sd_pid_notify_with_fds(pid, unset_environment, state, NULL, 0);
 }
diff --git a/src/notify/notify.c b/src/notify/notify.c
index 6c2dedd53fd6f..69d473401da66 100644
--- a/src/notify/notify.c
+++ b/src/notify/notify.c
@@ -18,6 +18,7 @@
 #include "string-util.h"
 #include "strv.h"
 #include "terminal-util.h"
+#include "time-util.h"
 #include "user-util.h"
 #include "util.h"
 
@@ -27,6 +28,7 @@ static const char *arg_status = NULL;
 static bool arg_booted = false;
 static uid_t arg_uid = UID_INVALID;
 static gid_t arg_gid = GID_INVALID;
+static bool arg_no_block = false;
 
 static int help(void) {
         _cleanup_free_ char *link = NULL;
@@ -45,6 +47,7 @@ static int help(void) {
                "     --uid=USER        Set user to send from\n"
                "     --status=TEXT     Set status text\n"
                "     --booted          Check if the system was booted up with systemd\n"
+               "     --no-block        Do not wait until operation finished\n"
                "\nSee the %s for details.\n"
                , program_invocation_short_name
                , ansi_highlight(), ansi_normal()
@@ -83,6 +86,7 @@ static int parse_argv(int argc, char *argv[]) {
                 ARG_STATUS,
                 ARG_BOOTED,
                 ARG_UID,
+                ARG_NO_BLOCK
         };
 
         static const struct option options[] = {
@@ -93,6 +97,7 @@ static int parse_argv(int argc, char *argv[]) {
                 { "status",    required_argument, NULL, ARG_STATUS    },
                 { "booted",    no_argument,       NULL, ARG_BOOTED    },
                 { "uid",       required_argument, NULL, ARG_UID       },
+                { "no-block",  no_argument,       NULL, ARG_NO_BLOCK  },
                 {}
         };
 
@@ -157,6 +162,10 @@ static int parse_argv(int argc, char *argv[]) {
                         break;
                 }
 
+                case ARG_NO_BLOCK:
+                        arg_no_block = true;
+                        break;
+
                 case '?':
                         return -EINVAL;
 
@@ -256,6 +265,16 @@ static int run(int argc, char* argv[]) {
         if (r == 0)
                 return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP),
                                        "No status data could be sent: $NOTIFY_SOCKET was not set");
+
+        if (!arg_no_block) {
+                r = sd_notify_barrier(0, 5 * USEC_PER_SEC);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to invoke barrier: %m");
+                if (r == 0)
+                        return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP),
+                                               "No status data could be sent: $NOTIFY_SOCKET was not set");
+        }
+
         return 0;
 }
 
diff --git a/src/systemd/sd-daemon.h b/src/systemd/sd-daemon.h
index 62b0f723c7a1a..b47b15a445a96 100644
--- a/src/systemd/sd-daemon.h
+++ b/src/systemd/sd-daemon.h
@@ -286,6 +286,19 @@ int sd_pid_notifyf(pid_t pid, int unset_environment, const char *format, ...) _s
 */
 int sd_pid_notify_with_fds(pid_t pid, int unset_environment, const char *state, const int *fds, unsigned n_fds);
 
+/*
+  Returns > 0 if synchronization with systemd succeeded.  Returns < 0
+  on error. Returns 0 if $NOTIFY_SOCKET was not set. Note that the
+  timeout parameter of this function call takes the timeout in µs, and
+  will be passed to ppoll(2), hence the behaviour will be similar to
+  ppoll(2). This function can be called after sending a status message
+  to systemd, if one needs to synchronize against reception of the
+  status messages sent before this call is made. Therefore, this
+  cannot be used to know if the status message was processed
+  successfully, but to only synchronize against its consumption.
+*/
+int sd_notify_barrier(int unset_environment, uint64_t timeout);
+
 /*
   Returns > 0 if the system was booted with systemd. Returns < 0 on
   error. Returns 0 if the system was not booted with systemd. Note