diff --git a/include/mbedtls/chacha20.h b/include/mbedtls/chacha20.h
index 579ea38..7a8cd53 100644
--- a/include/mbedtls/chacha20.h
+++ b/include/mbedtls/chacha20.h
@@ -42,7 +42,8 @@
 #include <stdint.h>
 #include <stddef.h>
 
-#define MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA -0x003B /**< Invalid input parameter(s). */
+#define MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA         -0x0053 /**< Invalid input parameter(s). */
+#define MBEDTLS_ERR_CHACHA20_FEATURE_UNAVAILABLE    -0x0055 /**< Feature not available. For example, s part of the API is not implemented. */
 
 #ifdef __cplusplus
 extern "C" {