diff --git a/koha-tmpl/intranet-tmpl/prog/en/modules/members/memberentrygen.tt b/koha-tmpl/intranet-tmpl/prog/en/modules/members/memberentrygen.tt
index 5453bc0294..feecd017e1 100644
--- a/koha-tmpl/intranet-tmpl/prog/en/modules/members/memberentrygen.tt
+++ b/koha-tmpl/intranet-tmpl/prog/en/modules/members/memberentrygen.tt
@@ -1971,6 +1971,9 @@ legend:hover {
         [% IF guarantor_attributes %]
             guarantor_attributes = [% To.json(guarantor_attributes) %];
         [% END %]
+        [% IF to_api_mapping %]
+            to_api_mapping = [% To.json(to_api_mapping) %];
+        [% END %]
 
         var TalkingTechItivaPhoneNotification = [% Koha.Preference('TalkingTechItivaPhoneNotification') || 0 | html %];
         var PhoneNotification = [% Koha.Preference('PhoneNotification') || 0 | html %];
diff --git a/koha-tmpl/intranet-tmpl/prog/js/members.js b/koha-tmpl/intranet-tmpl/prog/js/members.js
index 08e130fee9..131c1b514d 100644
--- a/koha-tmpl/intranet-tmpl/prog/js/members.js
+++ b/koha-tmpl/intranet-tmpl/prog/js/members.js
@@ -122,16 +122,17 @@ function select_user(borrowernumber, borrower, relationship) {
             fieldset.find('.new_guarantor_relationship').val(relationship);
         }
 
-        if(typeof guarantor_attributes !== 'undefined') {
+        if(typeof guarantor_attributes !== 'undefined' && to_api_mapping) {
             $.ajax({
                 url: '/api/v1/patrons/'+borrowernumber,
                 method: "GET",
                 dataType: 'json',
                 success: function(data){
-                    for (var i = 0; i < parseInt(guarantor_attributes.length, 10); i++) {
-                        var attribute = guarantor_attributes[i];
-                        if ( data[attribute] != null && document.forms.entryform[attribute].value == "" ) {
-                            document.forms.entryform[attribute].value = data[attribute];
+                    for (let i = 0; i < parseInt(guarantor_attributes.length, 10); i++) {
+                        let attribute = guarantor_attributes[i];
+                        let key_data = to_api_mapping[attribute] || attribute;
+                        if(data[key_data] != null && attribute in document.forms.entryform && document.forms.entryform[attribute].value == ""){
+                            document.forms.entryform[attribute].value = data[key_data];
                         }
                     }
                 }
diff --git a/members/memberentry.pl b/members/memberentry.pl
index 29955a4694..dbdb651150 100755
--- a/members/memberentry.pl
+++ b/members/memberentry.pl
@@ -618,7 +618,10 @@ if (C4::Context->preference("IndependentBranches")) {
 # Define the fields to be pre-filled in guarantee records
 my $prefillguarantorfields=C4::Context->preference("PrefillGuaranteeField");
 my @prefill_fields=split(/\,/,$prefillguarantorfields);
-$template->param( guarantor_attributes => \@prefill_fields );
+$template->param(
+    guarantor_attributes => \@prefill_fields,
+    to_api_mapping => Koha::Patron->new->to_api_mapping
+);
 
 if ($op eq 'add_form'){
     if ($guarantor_id) {