diff --git a/src/interpret/interpret.rs b/src/interpret/interpret.rs
index 921a308..10cdfd9 100644
--- a/src/interpret/interpret.rs
+++ b/src/interpret/interpret.rs
@@ -134,6 +134,7 @@ fn eval_expr(expr_env: &Env, state: &mut State, expr: &ast::Expr) -> Result<ast:
                 let closure_env: Env = state.envs.get(env)?.clone();
                 eval_expr(&closure_env, state, expr)
             }
+            ast::Value::Ref(reference) => Ok(state.variables.get(reference).clone()),
             _ => Ok(v.clone()),
         },
         ast::Expr::Op { lhs, rhs, op } => match op {
@@ -143,7 +144,7 @@ fn eval_expr(expr_env: &Env, state: &mut State, expr: &ast::Expr) -> Result<ast:
                     state.variables.set(reference, rhs.clone());
                     Ok(rhs)
                 }
-                _ => todo!(),
+                v => Err(Error::NotAReference(v.clone())),
             },
             /*
             _ => {