diff --git a/schala-lang/language/src/reduced_ir/test.rs b/schala-lang/language/src/reduced_ir/test.rs
index 7b3c56c..3cd7197 100644
--- a/schala-lang/language/src/reduced_ir/test.rs
+++ b/schala-lang/language/src/reduced_ir/test.rs
@@ -38,5 +38,6 @@ fn test_ir() {
     "#;
 
     let reduced = build_ir(src);
-    assert!(1 == 2);
+    assert_eq!(reduced.functions.len(), 3);
+    //assert!(1 == 2);
 }
diff --git a/schala-lang/language/src/tree_walk_eval/mod.rs b/schala-lang/language/src/tree_walk_eval/mod.rs
index e8561ca..e6c3bc6 100644
--- a/schala-lang/language/src/tree_walk_eval/mod.rs
+++ b/schala-lang/language/src/tree_walk_eval/mod.rs
@@ -130,6 +130,12 @@ enum Primitive {
     */
 }
 
+impl Primitive {
+    fn unit() -> Self {
+        Primitive::Tuple(vec![])
+    }
+}
+
 impl From<Literal> for Primitive {
     fn from(lit: Literal) -> Self {
         Primitive::Literal(lit)
@@ -240,9 +246,9 @@ impl<'a> State<'a> {
           },
           Expression::Assign { ref lval, box rval } => {
               let mem = lval.into();
-              let _ = rval;
-              let _env = self.environments.lookup(&mem);
-              return Err("Assign not implemented".into());
+              let evaluated = self.expression(rval)?;
+              self.environments.insert(mem, RuntimeValue::Primitive(evaluated));
+              Primitive::unit()
           },
           Expression::Call { box f, args } => self.call_expression(f, args)?,
           Expression::Callable(func) => Primitive::Callable(func),
diff --git a/schala-lang/language/src/tree_walk_eval/test.rs b/schala-lang/language/src/tree_walk_eval/test.rs
index e919e37..d1bea6f 100644
--- a/schala-lang/language/src/tree_walk_eval/test.rs
+++ b/schala-lang/language/src/tree_walk_eval/test.rs
@@ -20,7 +20,7 @@ fn eval_assert(input: &str, expected: &str) {
 #[test]
 fn test_basic_eval() {
   eval_assert("1 + 2", "3");
-  //eval_assert("let mut a = 1; a = 2", "()");
+  eval_assert("let mut a = 1; a = 2", "()");
   /*
      test_in_fresh_env!("let mut a = 1; a = 2; a", "2");
      test_in_fresh_env!(r#"("a", 1 + 2)"#, r#"("a", 3)"#);