diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 7c9acb2..4c8fc3c 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -274,6 +274,7 @@
 //#define MBEDTLS_BLOWFISH_ALT
 //#define MBEDTLS_CAMELLIA_ALT
 //#define MBEDTLS_CCM_ALT
+//#define MBEDTLS_CHACHA20_ALT
 //#define MBEDTLS_CMAC_ALT
 //#define MBEDTLS_DES_ALT
 //#define MBEDTLS_DHM_ALT
@@ -1862,6 +1863,15 @@
 #define MBEDTLS_CERTS_C
 
 /**
+ * \def MBEDTLS_CHACHA20_C
+ *
+ * Enable the ChaCha20 stream cipher.
+ *
+ * Module:  library/chacha20.c
+ */
+#define MBEDTLS_CHACHA20_C
+
+/**
  * \def MBEDTLS_CIPHER_C
  *
  * Enable the generic cipher layer.