diff --git a/fine/src/semantics.rs b/fine/src/semantics.rs
index 03746659..77de0afa 100644
--- a/fine/src/semantics.rs
+++ b/fine/src/semantics.rs
@@ -401,6 +401,22 @@ impl<'a> Semantics<'a> {
             TreeKind::LetStatement => self.environment_of_let(parent, tree),
             TreeKind::FunctionDecl => self.environment_of_func(parent, tree),
 
+            // TODO: Blocks should introduce a local environment if required.
+            //       Test with a type error in a block statement and a
+            //       binding outside. You will need a new assertion type and
+            //       possibly a compile/run to ensure it works.
+            //
+            //  let x = 7;
+            //  {
+            //    let x = 23;
+            //  }
+            //  print(x); // 7
+            //
+            //  {
+            //     let y = 12; // check: `y` is local not global!
+            //  }
+            //  print(y); // error, cannot find 'y'
+
             // TODO: MORE Things that introduce an environment!
             _ => parent,
         };