diff --git a/schala-lang/language/src/ast/visitor.rs b/schala-lang/language/src/ast/visitor.rs
index abd3ad7..2374cff 100644
--- a/schala-lang/language/src/ast/visitor.rs
+++ b/schala-lang/language/src/ast/visitor.rs
@@ -4,8 +4,8 @@ use crate::ast::*;
 //TODO maybe these functions should take closures that return a KeepRecursing | StopHere type,
 //or a tuple of (T, <that type>)
 
-pub trait ASTVisitor: Sized {
-  type BlockHandler: BlockVisitor = ();
+pub trait ASTVisitor<BlockHandler=()>: Sized {
+  type BlockHandler: BlockVisitor;
   fn ast(&mut self, _ast: &AST) {}
   fn block(&mut self) -> Self::BlockHandler { Self::BlockHandler::new() }
   fn block_finished(&mut self, handler: Self::BlockHandler) {}