diff --git a/ff_derive/src/lib.rs b/ff_derive/src/lib.rs
index 53bc6ea..198d89e 100644
--- a/ff_derive/src/lib.rs
+++ b/ff_derive/src/lib.rs
@@ -1189,7 +1189,7 @@ fn prime_field_impl(
         impl ::ff::PrimeField for #name {
             type Repr = #repr;
 
-            fn from_repr(r: #repr) -> ::ff::derive::subtle::CtOption<#name> {
+            fn from_repr(r: &#repr) -> ::ff::derive::subtle::CtOption<#name> {
                 #from_repr_impl
 
                 // Try to subtract the modulus
@@ -1207,7 +1207,7 @@ fn prime_field_impl(
                 ::ff::derive::subtle::CtOption::new(r * &R2, is_some)
             }
 
-            fn from_repr_vartime(r: #repr) -> Option<#name> {
+            fn from_repr_vartime(r: &#repr) -> Option<#name> {
                 #from_repr_impl
 
                 if r.is_valid() {
diff --git a/src/lib.rs b/src/lib.rs
index 4ffb982..8fca835 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -280,7 +280,7 @@ pub trait PrimeField: Field + From<u64> {
     ///
     /// The byte representation is interpreted with the same endianness as elements
     /// returned by [`PrimeField::to_repr`].
-    fn from_repr(repr: Self::Repr) -> CtOption<Self>;
+    fn from_repr(repr: &Self::Repr) -> CtOption<Self>;
 
     /// Attempts to convert a byte representation of a field element into an element of
     /// this prime field, failing if the input is not canonical (is not smaller than the
@@ -293,7 +293,7 @@ pub trait PrimeField: Field + From<u64> {
     ///
     /// This method provides **no** constant-time guarantees. Implementors of the
     /// `PrimeField` trait **may** optimise this method using non-constant-time logic.
-    fn from_repr_vartime(repr: Self::Repr) -> Option<Self> {
+    fn from_repr_vartime(repr: &Self::Repr) -> Option<Self> {
         Self::from_repr(repr).into()
     }