diff --git a/library/bignum_mod.c b/library/bignum_mod.c
index 9b0f6ec..ba661e2 100644
--- a/library/bignum_mod.c
+++ b/library/bignum_mod.c
@@ -138,31 +138,15 @@
 
 int mbedtls_mpi_mod_modulus_setup(mbedtls_mpi_mod_modulus *N,
                                   const mbedtls_mpi_uint *p,
-                                  size_t p_limbs,
-                                  mbedtls_mpi_mod_rep_selector int_rep)
+                                  size_t p_limbs)
 {
     int ret = 0;
-
     N->p = p;
     N->limbs = p_limbs;
     N->bits = mbedtls_mpi_core_bitlen(p, p_limbs);
-
-    switch (int_rep) {
-        case MBEDTLS_MPI_MOD_REP_MONTGOMERY:
-            N->int_rep = int_rep;
-            N->rep.mont.mm = mbedtls_mpi_core_montmul_init(N->p);
-            ret = set_mont_const_square(&N->rep.mont.rr, N->p, N->limbs);
-            break;
-        case MBEDTLS_MPI_MOD_REP_OPT_RED:
-            N->int_rep = int_rep;
-            N->rep.ored = NULL;
-            break;
-        default:
-            ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
-            goto exit;
-    }
-
-exit:
+    N->int_rep = MBEDTLS_MPI_MOD_REP_MONTGOMERY;
+    N->rep.mont.mm = mbedtls_mpi_core_montmul_init(N->p);
+    ret = set_mont_const_square(&N->rep.mont.rr, N->p, N->limbs);
 
     if (ret != 0) {
         mbedtls_mpi_mod_modulus_free(N);
@@ -248,8 +232,7 @@
     mbedtls_mpi_mod_modulus Nmont;
     mbedtls_mpi_mod_modulus_init(&Nmont);
 
-    MBEDTLS_MPI_CHK(mbedtls_mpi_mod_modulus_setup(&Nmont, N->p, N->limbs,
-                                                  MBEDTLS_MPI_MOD_REP_MONTGOMERY));
+    MBEDTLS_MPI_CHK(mbedtls_mpi_mod_modulus_setup(&Nmont, N->p, N->limbs));
 
     /* We'll use X->p to hold the Montgomery form of the input A->p */
     mbedtls_mpi_core_to_mont_rep(X->p, A->p, Nmont.p, Nmont.limbs,
diff --git a/library/bignum_mod.h b/library/bignum_mod.h
index 6c283b3..ccf86c0 100644
--- a/library/bignum_mod.h
+++ b/library/bignum_mod.h
@@ -197,16 +197,12 @@
  *                  not be modified in any way until after
  *                  mbedtls_mpi_mod_modulus_free() is called.
  * \param p_limbs   The number of limbs of \p p.
- * \param int_rep   The internal representation to be used for residues
- *                  associated with \p N (see #mbedtls_mpi_mod_rep_selector).
  *
  * \return      \c 0 if successful.
- * \return      #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if \p int_rep is invalid.
  */
 int mbedtls_mpi_mod_modulus_setup(mbedtls_mpi_mod_modulus *N,
                                   const mbedtls_mpi_uint *p,
-                                  size_t p_limbs,
-                                  mbedtls_mpi_mod_rep_selector int_rep);
+                                  size_t p_limbs);
 
 /** Setup an optimised-reduction compatible modulus structure.
  *
diff --git a/library/ecp_curves.c b/library/ecp_curves.c
index af649a2..69091c3 100644
--- a/library/ecp_curves.c
+++ b/library/ecp_curves.c
@@ -6003,8 +6003,7 @@
             return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
     }
 
-    if (mbedtls_mpi_mod_modulus_setup(N, p, p_limbs,
-                                      MBEDTLS_MPI_MOD_REP_MONTGOMERY)) {
+    if (mbedtls_mpi_mod_modulus_setup(N, p, p_limbs)) {
         return MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     }
     return 0;