diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index 1c60ec8..31523db 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -2423,6 +2423,9 @@
  *
  * Enable the generic message digest layer.
  *
+ * 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
  * Caller:  library/constant_time.c
  *          library/ecdsa.c