diff --git a/src/org/rascalmpl/library/lang/rascal/tests/concrete/Syntax3.rsc b/src/org/rascalmpl/library/lang/rascal/tests/concrete/Syntax3.rsc
index 7a51d029e6c..0d267360dce 100644
--- a/src/org/rascalmpl/library/lang/rascal/tests/concrete/Syntax3.rsc
+++ b/src/org/rascalmpl/library/lang/rascal/tests/concrete/Syntax3.rsc
@@ -8,8 +8,8 @@ syntax Aas
   | aas: [a][a][a]*
   ;
   
-Aas ambFilter(amb(set[Aas] alternatives)) {
-  set[Aas] result = {a | Aas a <- alternatives, !(a is nil)};
+&T <: Tree ambFilter(amb(set[&T <: Tree] alternatives)) {
+  set[&T <: Tree] result = {a | &T <: Tree a <- alternatives, !(a is nil)};
   
   if ({oneTree} := result) {
     return oneTree;