diff --git a/about.pl b/about.pl
index 339f4e2820..4fbc7e89d4 100755
--- a/about.pl
+++ b/about.pl
@@ -84,12 +84,18 @@ if ( ! defined C4::Context->config('zebra_bib_index_mode') ) {
     push @xml_config_warnings, {
         error => 'zebra_bib_index_mode_warn'
     };
+} else {
+    push @xml_config_warnings, { error => 'zebra_bib_grs_warn' }
+        if C4::Context->config('zebra_bib_index_mode') eq 'grs1';
 }
 
 if ( ! defined C4::Context->config('zebra_auth_index_mode') ) {
     push @xml_config_warnings, {
         error => 'zebra_auth_index_mode_warn'
     };
+} else {
+    push @xml_config_warnings, { error => 'zebra_auth_grs_warn' }
+        if C4::Context->config('zebra_auth_index_mode') eq 'grs1';
 }
 
 # Test QueryParser configuration sanity
diff --git a/koha-tmpl/intranet-tmpl/prog/en/modules/about.tt b/koha-tmpl/intranet-tmpl/prog/en/modules/about.tt
index 75a367db37..6e87b375f2 100644
--- a/koha-tmpl/intranet-tmpl/prog/en/modules/about.tt
+++ b/koha-tmpl/intranet-tmpl/prog/en/modules/about.tt
@@ -145,9 +145,39 @@
                 <caption>XML configuration file</caption>
             [% FOREACH config_entry IN xml_config_warnings %]
                 [% IF config_entry.error == 'zebra_bib_index_mode_warn' %]
-                <tr><th scope="row"><b>Warning</b> </th><td>The &lt;zebra_bib_index_mode&gt; entry is missing in your configuration file. It should be set to <strong>dom</strong> or <strong>grs1</strong>. It will default to <strong>grs1</strong> but this could change in the future.</td></tr>
+                <tr>
+                    <th scope="row"><b>Warning</b></th>
+                    <td>The &lt;zebra_bib_index_mode&gt; entry is missing in your configuration file.
+                        It should be set to <strong>dom</strong> or <strong>grs1</strong> (deprecated).
+                        It will default to <strong>dom</strong>.
+                    </td>
+                </tr>
                 [% ELSIF config_entry.error == 'zebra_auth_index_mode_warn' %]
-                <tr><th scope="row"><b>Warning</b> </th><td>The &lt;zebra_auth_index_mode&gt; entry is missing in your configuration file. It should be set to <strong>dom</strong> or <strong>grs1</strong>. It will default to <strong>dom</strong> but this could change in the future.</td></tr>
+                <tr>
+                    <th scope="row"><b>Warning</b></th>
+                    <td>The &lt;zebra_auth_index_mode&gt; entry is missing in your configuration file.
+                        It should be set to <strong>dom</strong> or <strong>grs1</strong> (deprecated).
+                        It will default to <strong>dom</strong>.
+                    </td>
+                </tr>
+                [% ELSIF config_entry.error == 'zebra_bib_grs_warn' %]
+                <tr>
+                    <th scope="row"><b>Warning</b></th>
+                    <td>The &lt;zebra_bib_index_mode&gt; entry is set to <strong>grs1</strong>.
+                        GRS-1 support is now deprecated and will be removed in future releases.
+                        Please use DOM instead by setting &lt;zebra_bib_index_mode&gt; to
+                        <strong>dom</strong> (full reindex required).
+                    </td>
+                </tr>
+                [% ELSIF config_entry.error == 'zebra_auth_grs_warn' %]
+                <tr>
+                    <th scope="row"><b>Warning</b></th>
+                    <td>The &lt;zebra_auth_index_mode&gt; entry is set to <strong>grs1</strong>.
+                        GRS-1 support is now deprecated and will be removed in future releases.
+                        Please use DOM instead by setting &lt;zebra_auth_index_mode&gt; to
+                        <strong>dom</strong> (full reindex required).
+                    </td>
+                </tr>
                 [% ELSIF config_entry.error == 'queryparser_entry_missing' %]
                 <tr>
                     <th scope="row"><b>Warning</b></th>