diff --git a/library/ecp_invasive.h b/library/ecp_invasive.h
index 8ea6ece..be9b399 100644
--- a/library/ecp_invasive.h
+++ b/library/ecp_invasive.h
@@ -98,21 +98,21 @@
 
 /** Fast quasi-reduction modulo p224 (FIPS 186-3 D.2.2)
  *
- * \param[in,out]   Np  The address of the MPI to be converted.
- *                      Must have exact limb size that stores a 448-bit MPI
- *                      (double the bitlength of the modulus).
- *                      Upon return holds the reduced value which is
- *                      in range `0 <= X < 2 * N` (where N is the modulus).
- *                      The bitlength of the reduced value is the same as
- *                      that of the modulus (224 bits).
- * \param[in]       Nn  The length of \p Nn in limbs.
+ * \param[in,out]   X       The address of the MPI to be converted.
+ *                          Must have exact limb size that stores a 448-bit MPI
+ *                          (double the bitlength of the modulus).
+ *                          Upon return holds the reduced value which is
+ *                          in range `0 <= X < 2 * N` (where N is the modulus).
+ *                          The bitlength of the reduced value is the same as
+ *                          that of the modulus (224 bits).
+ * \param[in]       X_limbs The length of \p X in limbs.
  *
  * \return          \c 0 on success.
- * \return          #MBEDTLS_ERR_ECP_BAD_INPUT_DATA if \p Nn is not the limb
- *                  size that sores a 448-bit MPI.
+ * \return          #MBEDTLS_ERR_ECP_BAD_INPUT_DATA if \p X_limbs is not the
+ *                  limb size that sores a 448-bit 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 /* MBEDTLS_ECP_DP_SECP224R1_ENABLED */