diff --git a/util/bigint/src/uint.rs b/util/bigint/src/uint.rs
index 3997d2e66..c18ed839c 100644
--- a/util/bigint/src/uint.rs
+++ b/util/bigint/src/uint.rs
@@ -36,6 +36,9 @@
 //! The functions here are designed to be fast.
 //!
 
+
+#[cfg(all(asm_available, target_arch="x86_64"))]
+use std::mem;
 use std::fmt;
 use std::cmp;