--- /usr/share/perl5/Lemonldap/NG/Portal/UserDB/LDAP.pm.old	2019-12-11 12:05:54.000000000 +0100
+++ /usr/share/perl5/Lemonldap/NG/Portal/UserDB/LDAP.pm	2021-01-05 10:54:19.188732119 +0100
@@ -40,10 +40,15 @@
         %{ $self->conf->{ldapExportedVars} } );
     while ( my ( $k, $v ) = each %vars ) {
 
+        my $value = $self->ldap->getLdapValue( $req->data->{ldapentry}, $v );
+
         # getLdapValue returns an empty string for missing attribute
         # but we really want to return undef so they don't get stored in session
-        $req->sessionInfo->{$k} =
-          $self->ldap->getLdapValue( $req->data->{ldapentry}, $v ) || undef;
+        # This has to be a string comparison because "0" is a valid attribute
+        # value. See #2403
+        $value = undef if ( $value eq "" );
+
+        $req->sessionInfo->{$k} = $value;
     }
 
     PE_OK;