diff --git a/include/mbedtls/blowfish.h b/include/mbedtls/blowfish.h
index eea6882..82b772a 100644
--- a/include/mbedtls/blowfish.h
+++ b/include/mbedtls/blowfish.h
@@ -41,7 +41,11 @@
 #define MBEDTLS_BLOWFISH_BLOCKSIZE   8          /* Blowfish uses 64 bit blocks */
 
 #define MBEDTLS_ERR_BLOWFISH_INVALID_KEY_LENGTH                -0x0016  /**< Invalid key length. */
+
+/* MBEDTLS_ERR_BLOWFISH_HW_ACCEL_FAILED is deprecated and should not be used.
+ */
 #define MBEDTLS_ERR_BLOWFISH_HW_ACCEL_FAILED                   -0x0017  /**< Blowfish hardware accelerator failed. */
+
 #define MBEDTLS_ERR_BLOWFISH_INVALID_INPUT_LENGTH              -0x0018  /**< Invalid data input length. */
 
 #ifdef __cplusplus