diff --git a/library/ecp_curves.c b/library/ecp_curves.c
index 6dd7ed3..8f79880 100644
--- a/library/ecp_curves.c
+++ b/library/ecp_curves.c
@@ -4576,7 +4576,7 @@
 #if defined(MBEDTLS_ECP_DP_SECP224R1_ENABLED)
 static int ecp_mod_p224(mbedtls_mpi *);
 MBEDTLS_STATIC_TESTABLE
-int mbedtls_ecp_mod_p224_raw(mbedtls_mpi_uint *Np, size_t Nn);
+int mbedtls_ecp_mod_p224_raw(mbedtls_mpi_uint *X, size_t X_limbs);
 #endif
 #if defined(MBEDTLS_ECP_DP_SECP256R1_ENABLED)
 static int ecp_mod_p256(mbedtls_mpi *);