diff --git a/tools/import_borrowers.pl b/tools/import_borrowers.pl
index 9ac994bc75..9738f19dc3 100755
--- a/tools/import_borrowers.pl
+++ b/tools/import_borrowers.pl
@@ -252,7 +252,7 @@ if ( $uploadborrowers && length($uploadborrowers) > 0 ) {
             # FIXME: fixup_cardnumber says to lock table, but the web interface doesn't so this doesn't either.
             # At least this is closer to AddMember than in members/memberentry.pl
             if (!$borrower{'cardnumber'}) {
-                $borrower{'cardnumber'} = fixup_cardnumber('');
+                $borrower{'cardnumber'} = fixup_cardnumber(undef);
             }
             if ($borrowernumber = AddMember(%borrower)) {
                 if ($extended) {