diff --git a/man/systemd.service.xml b/man/systemd.service.xml
index ee4d393756..3bd058f00b 100644
--- a/man/systemd.service.xml
+++ b/man/systemd.service.xml
@@ -223,7 +223,11 @@
                                 daemon. Use of this option is
                                 recommended for services where
                                 <varname>Type=</varname> is set to
-                                <option>forking</option>.</para>
+                                <option>forking</option>. systemd will
+                                read the PID of the main process of
+                                the daemon after start-up of the
+                                service. systemd will not write to the
+                                file configured here.</para>
                                 </listitem>
                         </varlistentry>
 
diff --git a/man/systemd.socket.xml b/man/systemd.socket.xml
index 1aea2f89b1..3b7581c545 100644
--- a/man/systemd.socket.xml
+++ b/man/systemd.socket.xml
@@ -113,6 +113,17 @@
                 <para>Socket units may be used to implement on-demand
                 starting of services, as well as parallelized starting
                 of services.</para>
+
+                <para>Note that the daemon software configured for
+                socket activation with socket units needs to be able
+                to accept sockets from systemd, either via systemd's
+                native socket passing interface (see
+                <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+                for details) or via the traditional
+                <citerefentry><refentrytitle>inetd</refentrytitle><manvolnum>8</manvolnum></citerefentry>-style
+                socket passing (i.e. sockets passed in via STDIN and
+                STDOUT, using <varname>StandardInput=socket</varname>
+                in the service file).</para>
         </refsect1>
 
         <refsect1>