diff --git a/exercises/alphametics/src/lib.rs b/exercises/alphametics/src/lib.rs
index f856a7aed..93a2f3646 100644
--- a/exercises/alphametics/src/lib.rs
+++ b/exercises/alphametics/src/lib.rs
@@ -1,5 +1,5 @@
 use std::collections::HashMap;
 
-pub fn solve(puzzle: &str) -> Option<HashMap<char, u8>> {
+pub fn solve(_: &str) -> Option<HashMap<char, u8>> {
     unimplemented!()
 }