diff --git a/include/mbedtls/x509_crt.h b/include/mbedtls/x509_crt.h
index 491343f..5943cfc 100644
--- a/include/mbedtls/x509_crt.h
+++ b/include/mbedtls/x509_crt.h
@@ -943,28 +943,6 @@
  */
 void mbedtls_x509write_crt_set_version(mbedtls_x509write_cert *ctx, int version);
 
-#if defined(MBEDTLS_BIGNUM_C) && !defined(MBEDTLS_DEPRECATED_REMOVED)
-/**
- * \brief           Set the serial number for a Certificate.
- *
- * \deprecated      This function is deprecated and will be removed in a
- *                  future version of the library. Please use
- *                  mbedtls_x509write_crt_set_serial_raw() instead.
- *
- * \note            Even though the MBEDTLS_BIGNUM_C guard looks redundant since
- *                  X509 depends on PK and PK depends on BIGNUM, this emphasizes
- *                  a direct dependency between X509 and BIGNUM which is going
- *                  to be deprecated in the future.
- *
- * \param ctx       CRT context to use
- * \param serial    serial number to set
- *
- * \return          0 if successful
- */
-int MBEDTLS_DEPRECATED mbedtls_x509write_crt_set_serial(
-    mbedtls_x509write_cert *ctx, const mbedtls_mpi *serial);
-#endif // MBEDTLS_BIGNUM_C && !MBEDTLS_DEPRECATED_REMOVED
-
 /**
  * \brief           Set the serial number for a Certificate.
  *
diff --git a/library/x509write_crt.c b/library/x509write_crt.c
index 8bce1cc..4bae0fb 100644
--- a/library/x509write_crt.c
+++ b/library/x509write_crt.c
@@ -92,30 +92,6 @@
     return mbedtls_x509_string_to_names(&ctx->issuer, issuer_name);
 }
 
-#if defined(MBEDTLS_BIGNUM_C) && !defined(MBEDTLS_DEPRECATED_REMOVED)
-int mbedtls_x509write_crt_set_serial(mbedtls_x509write_cert *ctx,
-                                     const mbedtls_mpi *serial)
-{
-    int ret;
-    size_t tmp_len;
-
-    /* Ensure that the MPI value fits into the buffer */
-    tmp_len = mbedtls_mpi_size(serial);
-    if (tmp_len > MBEDTLS_X509_RFC5280_MAX_SERIAL_LEN) {
-        return MBEDTLS_ERR_X509_BAD_INPUT_DATA;
-    }
-
-    ctx->serial_len = tmp_len;
-
-    ret = mbedtls_mpi_write_binary(serial, ctx->serial, tmp_len);
-    if (ret < 0) {
-        return ret;
-    }
-
-    return 0;
-}
-#endif // MBEDTLS_BIGNUM_C && !MBEDTLS_DEPRECATED_REMOVED
-
 int mbedtls_x509write_crt_set_serial_raw(mbedtls_x509write_cert *ctx,
                                          unsigned char *serial, size_t serial_len)
 {