diff --git a/src/librustc_data_structures/unify/tests.rs b/src/librustc_data_structures/unify/tests.rs
index dbe3cfc7a48a..089e629a569d 100644
--- a/src/librustc_data_structures/unify/tests.rs
+++ b/src/librustc_data_structures/unify/tests.rs
@@ -12,7 +12,6 @@
 
 extern crate test;
 use self::test::Bencher;
-use std::collections::HashSet;
 use unify::{UnifyKey, UnificationTable};
 
 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]