diff --git a/src/lib/crypto/kimchi_backend/common/dune b/src/lib/crypto/kimchi_backend/common/dune
index 3d75a75b7ca..9a7cb8b8c91 100644
--- a/src/lib/crypto/kimchi_backend/common/dune
+++ b/src/lib/crypto/kimchi_backend/common/dune
@@ -25,6 +25,7 @@
   base.caml
   ppx_inline_test.config
   bignum.bigint
+  zarith
   base.base_internalhash_types
   ;; local libraries
   tuple_lib
diff --git a/src/lib/crypto/kimchi_backend/common/field.ml b/src/lib/crypto/kimchi_backend/common/field.ml
index 91d76aa71ff..12261d7b9f5 100644
--- a/src/lib/crypto/kimchi_backend/common/field.ml
+++ b/src/lib/crypto/kimchi_backend/common/field.ml
@@ -37,6 +37,8 @@ module type Input_intf = sig
 
   val is_square : t -> bool
 
+  val compare : t -> t -> int
+
   val equal : t -> t -> bool
 
   val print : t -> unit
@@ -177,24 +179,22 @@ module Make (F : Input_intf) :
             let of_sexpable = of_bigint
           end)
 
-      let to_bignum_bigint n =
-        let rec go i two_to_the_i acc =
-          if Int.equal i size_in_bits then acc
+      let to_bignum_bigint =
+        let zero = of_int 0 in
+        let one = of_int 1 in
+        fun n ->
+          if equal n zero then Bignum_bigint.zero
+          else if equal n one then Bignum_bigint.one
           else
-            let acc' =
-              if Bigint.test_bit n i then Bignum_bigint.(acc + two_to_the_i)
-              else acc
-            in
-            go (i + 1) Bignum_bigint.(two_to_the_i + two_to_the_i) acc'
-        in
-        go 0 Bignum_bigint.one Bignum_bigint.zero
+            Bytes.unsafe_to_string
+              ~no_mutation_while_string_reachable:(to_bytes n)
+            |> Z.of_bits |> Bignum_bigint.of_zarith_bigint
 
-      let hash_fold_t s x =
-        Bignum_bigint.hash_fold_t s (to_bignum_bigint (to_bigint x))
+      let hash_fold_t s x = Bignum_bigint.hash_fold_t s (to_bignum_bigint x)
 
       let hash = Hash.of_fold hash_fold_t
 
-      let compare t1 t2 = Bigint.compare (to_bigint t1) (to_bigint t2)
+      let compare = compare
 
       let equal = equal
 
diff --git a/src/lib/crypto/kimchi_backend/kimchi_backend.mli b/src/lib/crypto/kimchi_backend/kimchi_backend.mli
index b2fb42a082b..eb9baab3a9d 100644
--- a/src/lib/crypto/kimchi_backend/kimchi_backend.mli
+++ b/src/lib/crypto/kimchi_backend/kimchi_backend.mli
@@ -11,8 +11,6 @@ module Kimchi_backend_common : sig
 
       val sexp_of_t : t -> Sexplib0.Sexp.t
 
-      val compare : t -> t -> int
-
       val bin_size_t : t Bin_prot.Size.sizer
 
       val bin_write_t : t Bin_prot.Write.writer
@@ -56,6 +54,8 @@ module Kimchi_backend_common : sig
 
       val is_square : t -> bool
 
+      val compare : t -> t -> int
+
       val equal : t -> t -> bool
 
       val print : t -> unit
diff --git a/src/lib/crypto/kimchi_bindings/stubs/src/arkworks/pasta_fp.rs b/src/lib/crypto/kimchi_bindings/stubs/src/arkworks/pasta_fp.rs
index 3d9144f1303..08264921088 100644
--- a/src/lib/crypto/kimchi_bindings/stubs/src/arkworks/pasta_fp.rs
+++ b/src/lib/crypto/kimchi_bindings/stubs/src/arkworks/pasta_fp.rs
@@ -31,7 +31,7 @@ impl CamlFp {
     unsafe extern "C" fn ocaml_compare(x: ocaml::Raw, y: ocaml::Raw) -> i32 {
         let x = x.as_pointer::<Self>();
         let y = y.as_pointer::<Self>();
-        match x.as_ref().0.cmp(&y.as_ref().0) {
+        match x.as_ref().0.into_repr().cmp(&y.as_ref().0.into_repr()) {
             core::cmp::Ordering::Less => -1,
             core::cmp::Ordering::Equal => 0,
             core::cmp::Ordering::Greater => 1,
@@ -240,7 +240,7 @@ pub fn caml_pasta_fp_mut_square(mut x: ocaml::Pointer<CamlFp>) {
 #[ocaml_gen::func]
 #[ocaml::func]
 pub fn caml_pasta_fp_compare(x: ocaml::Pointer<CamlFp>, y: ocaml::Pointer<CamlFp>) -> ocaml::Int {
-    match x.as_ref().0.cmp(&y.as_ref().0) {
+    match x.as_ref().0.into_repr().cmp(&y.as_ref().0.into_repr()) {
         Less => -1,
         Equal => 0,
         Greater => 1,
diff --git a/src/lib/crypto/kimchi_bindings/stubs/src/arkworks/pasta_fq.rs b/src/lib/crypto/kimchi_bindings/stubs/src/arkworks/pasta_fq.rs
index 8fbca9da595..bc81f5962a6 100644
--- a/src/lib/crypto/kimchi_bindings/stubs/src/arkworks/pasta_fq.rs
+++ b/src/lib/crypto/kimchi_bindings/stubs/src/arkworks/pasta_fq.rs
@@ -36,7 +36,7 @@ impl CamlFq {
     unsafe extern "C" fn ocaml_compare(x: ocaml::Raw, y: ocaml::Raw) -> i32 {
         let x = x.as_pointer::<Self>();
         let y = y.as_pointer::<Self>();
-        match x.as_ref().0.cmp(&y.as_ref().0) {
+        match x.as_ref().0.into_repr().cmp(&y.as_ref().0.into_repr()) {
             core::cmp::Ordering::Less => -1,
             core::cmp::Ordering::Equal => 0,
             core::cmp::Ordering::Greater => 1,
@@ -241,7 +241,7 @@ pub fn caml_pasta_fq_mut_square(mut x: ocaml::Pointer<CamlFq>) {
 #[ocaml_gen::func]
 #[ocaml::func]
 pub fn caml_pasta_fq_compare(x: ocaml::Pointer<CamlFq>, y: ocaml::Pointer<CamlFq>) -> ocaml::Int {
-    match x.as_ref().0.cmp(&y.as_ref().0) {
+    match x.as_ref().0.into_repr().cmp(&y.as_ref().0.into_repr()) {
         Less => -1,
         Equal => 0,
         Greater => 1,