diff --git a/include/mbedtls/cipher.h b/include/mbedtls/cipher.h
index 3ee2ab7..2789393 100644
--- a/include/mbedtls/cipher.h
+++ b/include/mbedtls/cipher.h
@@ -145,6 +145,8 @@
     MBEDTLS_CIPHER_CAMELLIA_128_CCM,     /**< Camellia cipher with 128-bit CCM mode. */
     MBEDTLS_CIPHER_CAMELLIA_192_CCM,     /**< Camellia cipher with 192-bit CCM mode. */
     MBEDTLS_CIPHER_CAMELLIA_256_CCM,     /**< Camellia cipher with 256-bit CCM mode. */
+    MBEDTLS_CIPHER_AES_128_XTS,          /**< AES 128-bit cipher in XTS block mode. */
+    MBEDTLS_CIPHER_AES_256_XTS,          /**< AES 256-bit cipher in XTS block mode. */
 } mbedtls_cipher_type_t;
 
 /** Supported cipher modes. */
@@ -158,6 +160,7 @@
     MBEDTLS_MODE_GCM,                    /**< The GCM cipher mode. */
     MBEDTLS_MODE_STREAM,                 /**< The stream cipher mode. */
     MBEDTLS_MODE_CCM,                    /**< The CCM cipher mode. */
+    MBEDTLS_MODE_XTS,                    /**< The XTS cipher mode. */
 } mbedtls_cipher_mode_t;
 
 /** Supported cipher padding types. */
@@ -273,7 +276,8 @@
     /** Number of Bytes that have not been processed yet. */
     size_t unprocessed_len;
 
-    /** Current IV or NONCE_COUNTER for CTR-mode. */
+    /** Current IV or NONCE_COUNTER for CTR-mode, data unit (or sector) number
+     * for XTS-mode. */
     unsigned char iv[MBEDTLS_MAX_IV_LENGTH];
 
     /** IV size in Bytes, for ciphers with variable-length IVs. */