diff --git a/tinysnark/src/arith.rs b/tinysnark/src/arith.rs
index bf106af..31d7815 100644
--- a/tinysnark/src/arith.rs
+++ b/tinysnark/src/arith.rs
@@ -12,9 +12,13 @@ extern "C" {
     fn tinysnark_fieldt_add(a: FieldT, b: FieldT) -> FieldT;
 }
 
+#[derive(Copy, Clone, Debug)]
+#[repr(simd)]
+struct EightBytes(u64);
+
 #[derive(Copy, Clone, Debug)]
 #[repr(C)]
-pub struct FieldT([u8; 32]);
+pub struct FieldT([u8; 32], [EightBytes; 0]);
 
 impl FieldT {
     #[inline(always)]
diff --git a/tinysnark/src/lib.rs b/tinysnark/src/lib.rs
index 83084cf..7c90b9f 100644
--- a/tinysnark/src/lib.rs
+++ b/tinysnark/src/lib.rs
@@ -1,4 +1,4 @@
-#![feature(box_syntax)]
+#![feature(box_syntax, repr_simd)]
 #![allow(improper_ctypes)]
 //#![cfg_attr(test, feature(test))]
 extern crate libc;