diff --git a/Cargo.toml b/Cargo.toml
index 835d289..c97e240 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "blake2-rfc"
-version = "0.2.8"
+version = "0.2.9"
 authors = ["Cesar Eduardo Barros <cesarb@cesarb.eti.br>"]
 description = "A pure Rust implementation of BLAKE2 based on the draft RFC."
 repository = "https://github.com/cesarb/blake2-rfc"
diff --git a/src/simd.rs b/src/simd.rs
index 68ae17e..8e7a0c2 100644
--- a/src/simd.rs
+++ b/src/simd.rs
@@ -31,13 +31,13 @@ use std::mem::transmute;
 pub use simdty::{u32x4, u64x4};
 
 #[cfg(not(feature = "simd"))]
-#[allow(non_camel_case_types)]
 #[derive(Clone, Copy, Debug)]
+#[repr(C)]
 pub struct u32x4(pub u32, pub u32, pub u32, pub u32);
 
 #[cfg(not(feature = "simd"))]
-#[allow(non_camel_case_types)]
 #[derive(Clone, Copy, Debug)]
+#[repr(C)]
 pub struct u64x4(pub u64, pub u64, pub u64, pub u64);
 
 #[cfg(not(feature = "simd"))]