diff --git a/koha-tmpl/intranet-tmpl/prog/en/modules/tools/import_borrowers.tt b/koha-tmpl/intranet-tmpl/prog/en/modules/tools/import_borrowers.tt
index fa955dac8b..f31d7dab84 100644
--- a/koha-tmpl/intranet-tmpl/prog/en/modules/tools/import_borrowers.tt
+++ b/koha-tmpl/intranet-tmpl/prog/en/modules/tools/import_borrowers.tt
@@ -90,6 +90,11 @@
                 [% IF ERROR.borrowernumber %] (for patron with borrowernumber [% ERROR.borrowernumber %])[% END %]
             </li>
         [% END %]
+        [% IF ERROR.duplicate_userid %]
+            <li class="line_error">
+                Userid [% ERROR.userid %] is already used by another patron or is empty.
+            </li>
+        [% END %]
     [% END %]
     </ul>
     </div>
diff --git a/tools/import_borrowers.pl b/tools/import_borrowers.pl
index 6a32611435..d5cf3b272b 100755
--- a/tools/import_borrowers.pl
+++ b/tools/import_borrowers.pl
@@ -253,6 +253,13 @@ if ( $uploadborrowers && length($uploadborrowers) > 0 ) {
             next;
         }
 
+        # generate a proper login if none provided
+        if ( $borrower{userid} eq '' || !Check_Userid( $borrower{userid} ) ) {
+            push @errors, { duplicate_userid => 1, userid => $borrower{userid} };
+            $invalid++;
+            next LINE;
+        }
+
 
         if ($borrowernumber) {
             # borrower exists