diff --git a/schala-lang/language/src/ast/walker.rs b/schala-lang/language/src/ast/walker.rs
index df370b9..112297b 100644
--- a/schala-lang/language/src/ast/walker.rs
+++ b/schala-lang/language/src/ast/walker.rs
@@ -78,6 +78,22 @@ fn call<V: ASTVisitor>(v: &mut V, f: &Expression, args: &Vec<InvocationArgument>
   v.expression(f);
   for arg in args.iter() {
     v.invocation_argument(arg);
+    invocation_argument(v, arg);
+  }
+}
+
+fn invocation_argument<V: ASTVisitor>(v: &mut V, arg: &InvocationArgument) {
+  use InvocationArgument::*;
+  match arg {
+    Positional(expr) => {
+      v.expression(expr);
+      expression(v, expr);
+    },
+    Keyword { expr, .. } => {
+      v.expression(expr);
+      expression(v, expr);
+    },
+    Ignored => (),
   }
 }