diff --git a/src/plfa/part1/Relations.lagda.md b/src/plfa/part1/Relations.lagda.md
index b9e3ab335..35460b45b 100644
--- a/src/plfa/part1/Relations.lagda.md
+++ b/src/plfa/part1/Relations.lagda.md
@@ -15,7 +15,7 @@ the next step is to define relations, such as _less than or equal_.
 ```agda
 import Relation.Binary.PropositionalEquality as Eq
 open Eq using (_≡_; refl; cong)
-open import Data.Nat using (ℕ; zero; suc; _+_)
+open import Data.Nat using (ℕ; zero; suc; _+_; _*_)
 open import Data.Nat.Properties using (+-comm; +-identityʳ)
 ```