diff --git a/man/sd_listen_fds.xml b/man/sd_listen_fds.xml
index 9fc06d730b3..7cd744e6c11 100644
--- a/man/sd_listen_fds.xml
+++ b/man/sd_listen_fds.xml
@@ -198,6 +198,9 @@
     number. <function>sd_listen_fds_with_names()</function> does the
     same but also parses <varname>$LISTEN_FDNAMES</varname> if
     set.</para>
+
+    <para>These functions are not designed for services that specify <varname>StandardInput=socket</varname>
+    as the <varname>$LISTEN_FDS</varname> variable is not set in their environment.</para>
   </refsect1>
 
   <refsect1>
diff --git a/man/systemd.exec.xml b/man/systemd.exec.xml
index a82868aeb12..e9cef24d182 100644
--- a/man/systemd.exec.xml
+++ b/man/systemd.exec.xml
@@ -2941,7 +2941,8 @@ SystemCallErrorNumber=EPERM</programlisting>
         input will be connected to the socket the service was activated from, which is primarily useful for
         compatibility with daemons designed for use with the traditional <citerefentry
         project='freebsd'><refentrytitle>inetd</refentrytitle><manvolnum>8</manvolnum></citerefentry> socket activation
-        daemon.</para>
+        daemon (<varname>$LISTEN_FDS</varname> (and related) environment variables are not passed when
+        <option>socket</option> value is configured).</para>
 
         <para>The <option>fd:<replaceable>name</replaceable></option> option connects standard input to a specific,
         named file descriptor provided by a socket unit. The name may be specified as part of this option, following a
diff --git a/sysctl.d/50-pid-max.conf b/sysctl.d/50-pid-max.conf
index 1eff2d7ecee..2beaf48f21f 100644
--- a/sysctl.d/50-pid-max.conf
+++ b/sysctl.d/50-pid-max.conf
@@ -11,6 +11,6 @@
 # (e.g. /etc/sysctl.d/90-override.conf), and put any assignments
 # there.
 
-# Bump the numeric PID range to its maximum of 2^22 (from the in-kernel default
-# of 2^16), to make PID collisions less likely.
+# Bump the numeric PID range to make PID collisions less likely.
+# 2^22 and 2^15 is possible maximum of 64bit and 32bit kernels respectively.
 kernel.pid_max = 4194304