diff --git a/library/ecp_curves.c b/library/ecp_curves.c
index 708dcec..c217c40 100644
--- a/library/ecp_curves.c
+++ b/library/ecp_curves.c
@@ -4623,7 +4623,7 @@
 #if defined(MBEDTLS_ECP_DP_SECP256K1_ENABLED)
 static int ecp_mod_p256k1(mbedtls_mpi *);
 MBEDTLS_STATIC_TESTABLE
-int mbedtls_ecp_mod_p256k1(mbedtls_mpi *);
+int mbedtls_ecp_mod_p256k1_raw(mbedtls_mpi_uint *X, size_t X_limbs);
 #endif
 
 #if defined(ECP_LOAD_GROUP)
@@ -5680,30 +5680,31 @@
 
 #if defined(MBEDTLS_ECP_DP_SECP256K1_ENABLED)
 
+/*
+ * Fast quasi-reduction modulo p256k1 = 2^256 - R,
+ * with R = 2^32 + 2^9 + 2^8 + 2^7 + 2^6 + 2^4 + 1 = 0x01000003D1
+ */
 static int ecp_mod_p256k1(mbedtls_mpi *N)
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     size_t expected_width = 2 * ((256 + biL - 1) / biL);
     MBEDTLS_MPI_CHK(mbedtls_mpi_grow(N, expected_width));
-    ret = mbedtls_ecp_mod_p256k1(N);
+    ret = mbedtls_ecp_mod_p256k1_raw(N->p, expected_width);
 
 cleanup:
     return ret;
 }
 
-/*
- * Fast quasi-reduction modulo p256k1 = 2^256 - R,
- * with R = 2^32 + 2^9 + 2^8 + 2^7 + 2^6 + 2^4 + 1 = 0x01000003D1
- */
 MBEDTLS_STATIC_TESTABLE
-int mbedtls_ecp_mod_p256k1(mbedtls_mpi *N)
+int mbedtls_ecp_mod_p256k1_raw(mbedtls_mpi_uint *X, size_t X_limbs)
 {
     static mbedtls_mpi_uint Rp[] = {
-        MBEDTLS_BYTES_TO_T_UINT_8(0xD1, 0x03, 0x00, 0x00, 0x01, 0x00, 0x00,
-                                  0x00)
+        MBEDTLS_BYTES_TO_T_UINT_8(0xD1, 0x03, 0x00, 0x00,
+                                  0x01, 0x00, 0x00, 0x00)
     };
-    return ecp_mod_koblitz(N->p, N->n, Rp, 256);
+    return ecp_mod_koblitz(X, X_limbs, Rp, 256);
 }
+
 #endif /* MBEDTLS_ECP_DP_SECP256K1_ENABLED */
 
 #if defined(MBEDTLS_TEST_HOOKS)