diff --git a/lib/NGCP/Panel/Role/API.pm b/lib/NGCP/Panel/Role/API.pm
index 412cb58f6e..f67e2bb72e 100644
--- a/lib/NGCP/Panel/Role/API.pm
+++ b/lib/NGCP/Panel/Role/API.pm
@@ -127,8 +127,19 @@ sub validate_form {
         }
     }
 
-    # remove unknown keys
-    my %fields = map { $_->name => $_ } $form->fields;
+    # remove unknown keys and prepare resource
+    my %fields;
+    foreach($form->fields){
+        if($_->readonly){
+            #Prepare resource for the PATCH considering readonly fields.
+            #PATCH is supposed to take full item content and so will get readonly fields into resource too. And apply patch.
+            #It leads to the situation when we may try to change some not existing fields in the DB
+            #All readonly fields are considered as representation only and should never be applied.
+            delete $resource->{$_->name};
+            next;
+        }
+        $fields{$_->name} = $_;
+    }
     $self->validate_fields($c, $resource, \%fields, $run);
 
     if($run) {
diff --git a/t/api-rest/api-customers-collection.t b/t/api-rest/api-customers-collection.t
index 8088fba0bd..05ad3db80a 100644
--- a/t/api-rest/api-customers-collection.t
+++ b/t/api-rest/api-customers-collection.t
@@ -56,6 +56,13 @@ SKIP:{
     #todo: create_timestamp - strange,  it is different to the value of the time zone
     $test_machine->check_get2put({ignore_fields => [qw/modify_timestamp create_timestamp/]});
 
+    my $mod_customer;
+    ($res,$mod_customer) = $test_machine->check_patch_correct( [ { op => 'replace', path => '/subscriber_email_template_id', value => undef } ] );
+    is($mod_customer->{subscriber_email_template_id}, undef,  "check patched subscriber_email_template_id:".($mod_customer->{subscriber_email_template_id} // 'undef'));
+
+    ($res,$mod_customer) = $test_machine->check_patch_correct( [ { op => 'replace', path => '/subscriber_email_template_id', value => $test_machine->DATA_ITEM->{subscriber_email_template_id} } ] );
+    is($mod_customer->{subscriber_email_template_id}, $test_machine->DATA_ITEM->{subscriber_email_template_id}, "check patched subscriber_email_template_id:".$mod_customer->{subscriber_email_template_id});
+
     $test_machine->check_bundle();
 }