diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index 9ae51c9..41a007e 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -2643,7 +2643,7 @@
 /**
  * \def MBEDTLS_MD_C
  *
- * Enable the generic message digest layer.
+ * Enable the generic layer for message digest (hashing) and HMAC.
  *
  * Requires: one of: MBEDTLS_MD5_C, MBEDTLS_RIPEMD160_C, MBEDTLS_SHA1_C,
  *                   MBEDTLS_SHA224_C, MBEDTLS_SHA256_C, MBEDTLS_SHA384_C,
@@ -2673,6 +2673,25 @@
 #define MBEDTLS_MD_C
 
 /**
+ * \def MBEDTLS_MD_LIGHT
+ *
+ * Enable the "light" subset of MBEDTLS_MD_C: just hashing and basic
+ * meta-data.
+ *
+ * This is automatically enabled whenever MBEDTLS_MD_C is enabled, but it is
+ * possible to enable this with MBEDTLS_MD_C if support for HMAC or extra
+ * metadata functions is not needed.
+ *
+ * Requires: one of: MBEDTLS_MD5_C, MBEDTLS_RIPEMD160_C, MBEDTLS_SHA1_C,
+ *                   MBEDTLS_SHA224_C, MBEDTLS_SHA256_C, MBEDTLS_SHA384_C,
+ *                   MBEDTLS_SHA512_C.
+ * Module:  library/md.c
+ *
+ * Uncomment to enabled the "light" subsect of MD.
+ */
+#define MBEDTLS_MD_LIGHT
+
+/**
  * \def MBEDTLS_MD5_C
  *
  * Enable the MD5 hash algorithm.