diff --git a/src/libsodium/include/sodium/crypto_sign_edwards25519sha512batch.h b/src/libsodium/include/sodium/crypto_sign_edwards25519sha512batch.h
index c0f595bf..4d556c83 100644
--- a/src/libsodium/include/sodium/crypto_sign_edwards25519sha512batch.h
+++ b/src/libsodium/include/sodium/crypto_sign_edwards25519sha512batch.h
@@ -1,6 +1,17 @@
 #ifndef crypto_sign_edwards25519sha512batch_H
 #define crypto_sign_edwards25519sha512batch_H
 
+/*
+ * WARNING: This construction was a prototype, which should not be used
+ * any more in new projects.
+ * 
+ * crypto_sign_edwards25519sha512batch is provided for applications
+ * initially built with NaCl, but as recommended by the author of this
+ * construction, new applications should use ed25519 instead.
+ * 
+ * In Sodium, you should use the high-level crypto_sign_*() functions instead.
+ */
+
 #include <stddef.h>
 #include "export.h"