diff --git a/man/systemd-nspawn.xml b/man/systemd-nspawn.xml
index e7c859d11..cab5990a5 100644
--- a/man/systemd-nspawn.xml
+++ b/man/systemd-nspawn.xml
@@ -133,6 +133,15 @@
                 <ulink
                 url="http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface">Container
                 Interface</ulink> specification.</para>
+
+                <para>As a safety check
+                <command>systemd-nspawn</command> will verify the
+                existance of <filename>/etc/os-release</filename> in
+                the container tree before starting the container (see
+                <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>). It
+                might be necessary to add this file to the container
+                tree manually if the OS of the container is too old to
+                contain this file out-of-the-box.</para>
         </refsect1>
 
         <refsect1>
diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index e907a1daa..f3568ab40 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -1285,7 +1285,7 @@ int main(int argc, char *argv[]) {
         }
 
         if (path_is_os_tree(arg_directory) <= 0) {
-                log_error("Directory %s doesn't look like an OS root directory. Refusing.", arg_directory);
+                log_error("Directory %s doesn't look like an OS root directory (/etc/os-release is missing). Refusing.", arg_directory);
                 goto finish;
         }