diff --git a/doc/configuration-file-required-settings.sgml b/doc/configuration-file-required-settings.sgml
index feff833c..f0cbe580 100644
--- a/doc/configuration-file-required-settings.sgml
+++ b/doc/configuration-file-required-settings.sgml
@@ -40,7 +40,8 @@
        to say the least.
      </para>
      <para>
-       Maximum length is 63 characters.
+       The string's maximum length is 63 characters and it should
+       contain only printable ASCII characters.
      </para>
     </listitem>
    </varlistentry>
diff --git a/repmgr.conf.sample b/repmgr.conf.sample
index faf929f1..5310bdeb 100644
--- a/repmgr.conf.sample
+++ b/repmgr.conf.sample
@@ -28,7 +28,8 @@
 				 # node's current role, e.g. 'primary' or 'standby1',
 				 # as roles can change and it will be confusing if
 				 # the current primary is called 'standby1'.
-                                 # Maximum length is 63 characters.
+                                 # The string's maximum length is 63 characters and it should
+                                 # contain only printable ASCII characters.
 
 #conninfo=''			 # Database connection information as a conninfo string.
 				 # All servers in the cluster must be able to connect to