diff --git a/koha-tmpl/intranet-tmpl/prog/en/modules/serials/subscription-frequencies.tt b/koha-tmpl/intranet-tmpl/prog/en/modules/serials/subscription-frequencies.tt
index d386f51d6f..02a1eed177 100644
--- a/koha-tmpl/intranet-tmpl/prog/en/modules/serials/subscription-frequencies.tt
+++ b/koha-tmpl/intranet-tmpl/prog/en/modules/serials/subscription-frequencies.tt
@@ -89,7 +89,8 @@
               </li>
               <li>
                 <label for="displayorder">Display order: </label>
-                <input type="text" id="displayorder" name="displayorder" value="[% displayorder | html %]" size="3" />
+                <input type="text" inputmode="numeric" pattern="\d*" id="displayorder" name="displayorder" value="[% displayorder | html %]" size="3" />
+                <span class="hint">Only numeric characters are allowed</span>
               </li>
             </ol>
           </fieldset>
diff --git a/serials/subscription-frequencies.pl b/serials/subscription-frequencies.pl
index 86d14fccd2..1cdcd0d47e 100755
--- a/serials/subscription-frequencies.pl
+++ b/serials/subscription-frequencies.pl
@@ -75,7 +75,8 @@ if($op && ($op eq 'savenew' || $op eq 'savemod')) {
     foreach (qw/ description unit issuesperunit unitsperissue displayorder /) {
         $frequency->{$_} = $input->param($_);
     }
-    $frequency->{unit} = undef if $frequency->{unit} eq '';
+    $frequency->{unit}         = undef if $frequency->{unit} eq '';
+    $frequency->{displayorder} = undef if $frequency->{displayorder} eq '';
     foreach (qw/issuesperunit unitsperissue/) {
         $frequency->{$_} = 1 if $frequency->{$_} !~ /\d+/;
     }