diff --git a/lemonldap-ng-manager/lib/Lemonldap/NG/Manager/Attributes.pm b/lemonldap-ng-manager/lib/Lemonldap/NG/Manager/Attributes.pm
index d9572bc73..3189ccd98 100644
--- a/lemonldap-ng-manager/lib/Lemonldap/NG/Manager/Attributes.pm
+++ b/lemonldap-ng-manager/lib/Lemonldap/NG/Manager/Attributes.pm
@@ -19,9 +19,10 @@ sub perlExpr {
     $cpt->reval("BEGIN { 'warnings'->unimport; } $val");
     my $err = join(
         '',
-        grep( { $_ =~ /Undefined subroutine/ ? () : $_; } split( /\n/, $@, 0 ) )
+        grep( { $_ =~ /(?:Undefined subroutine|Devel::StackTrace)/ ? () : $_; }
+            split( /\n/, $@, 0 ) )
     );
-    return $err ? ( 0, "__badExpression__: $err" ) : 1;
+    return $err ? ( -1, "__badExpression__: $err" ) : 1;
 }
 
 sub types {
diff --git a/lemonldap-ng-manager/lib/Lemonldap/NG/Manager/Build/Attributes.pm b/lemonldap-ng-manager/lib/Lemonldap/NG/Manager/Build/Attributes.pm
index a986b9686..028047fcf 100644
--- a/lemonldap-ng-manager/lib/Lemonldap/NG/Manager/Build/Attributes.pm
+++ b/lemonldap-ng-manager/lib/Lemonldap/NG/Manager/Build/Attributes.pm
@@ -25,8 +25,8 @@ sub perlExpr {
         $Lemonldap::NG::Common::Safelib::functions );
     $cpt->reval("BEGIN { 'warnings'->unimport; } $val");
     my $err = join( '',
-        grep { $_ =~ /Undefined subroutine/ ? () : $_ } split( /\n/, $@ ) );
-    return $err ? ( 0, "__badExpression__: $err" ) : (1);
+        grep { $_ =~ /(?:Undefined subroutine|Devel::StackTrace)/ ? () : $_ } split( /\n/, $@ ) );
+    return $err ? ( -1, "__badExpression__: $err" ) : (1);
 }
 
 my $url = $RE{URI}{HTTP}{ -scheme => "https?" };
diff --git a/lemonldap-ng-manager/lib/Lemonldap/NG/Manager/Conf/Parser.pm b/lemonldap-ng-manager/lib/Lemonldap/NG/Manager/Conf/Parser.pm
index c69b71b72..69f311bc5 100644
--- a/lemonldap-ng-manager/lib/Lemonldap/NG/Manager/Conf/Parser.pm
+++ b/lemonldap-ng-manager/lib/Lemonldap/NG/Manager/Conf/Parser.pm
@@ -1207,7 +1207,14 @@ sub _execTest {
     if ( $ref eq 'CODE' ) {
         my ( $r, $m ) = ( $test->( $value, $conf, $attr ) );
         if ($m) {
-            push @{ $self->{ ( $r ? 'warnings' : 'errors' ) } },
+            push @{
+                $self->{ (
+                        $r > 0
+                        ? 'warnings'
+                        : ( $r < 0 ? 'needConfirmation' : 'errors' )
+                    )
+                }
+              },
               { message => "$key: $m" };
         }
         elsif ( !$r ) {