diff --git a/src/field_32bit.rs b/src/field_32bit.rs
index ad85599..8a5cc12 100644
--- a/src/field_32bit.rs
+++ b/src/field_32bit.rs
@@ -56,7 +56,7 @@ use utils::{load3, load4};
 /// faster.  However, the `FieldElement64` implementation requires Rust's
 /// `u128`, which is not yet stable.
 #[derive(Copy, Clone)]
-pub struct FieldElement32(pub [i32; 10]);
+pub struct FieldElement32(pub (crate) [i32; 10]);
 
 impl Debug for FieldElement32 {
     fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
diff --git a/src/field_64bit.rs b/src/field_64bit.rs
index a4da3a0..9eb8f6e 100644
--- a/src/field_64bit.rs
+++ b/src/field_64bit.rs
@@ -51,7 +51,7 @@ pub type Limb = u64;
 /// which gives even better performance.  This implementation requires Rust's
 /// `u128`, which is not yet stable.
 #[derive(Copy, Clone)]
-pub struct FieldElement64(pub [u64; 5]);
+pub struct FieldElement64(pub (crate) [u64; 5]);
 
 impl Debug for FieldElement64 {
     fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {