diff --git a/src/libsodium/crypto_sign/crypto_sign.c b/src/libsodium/crypto_sign/crypto_sign.c
index 1f3b8560..81fb1b96 100644
--- a/src/libsodium/crypto_sign/crypto_sign.c
+++ b/src/libsodium/crypto_sign/crypto_sign.c
@@ -7,6 +7,12 @@ crypto_sign_bytes(void)
     return crypto_sign_BYTES;
 }
 
+size_t
+crypto_sign_seedbytes(void)
+{
+    return crypto_sign_SEEDBYTES;
+}
+
 size_t
 crypto_sign_publickeybytes(void)
 {
diff --git a/src/libsodium/crypto_sign/ed25519/ref10/api.h b/src/libsodium/crypto_sign/ed25519/ref10/api.h
index 87cd56e9..74309f7e 100644
--- a/src/libsodium/crypto_sign/ed25519/ref10/api.h
+++ b/src/libsodium/crypto_sign/ed25519/ref10/api.h
@@ -6,6 +6,7 @@
 #define crypto_sign_keypair crypto_sign_ed25519_keypair
 #define crypto_sign_seed_keypair crypto_sign_ed25519_seed_keypair
 #define crypto_sign_BYTES crypto_sign_ed25519_BYTES
+#define crypto_sign_SEEDBYTES crypto_sign_ed25519_SEEDBYTES
 #define crypto_sign_PUBLICKEYBYTES crypto_sign_ed25519_PUBLICKEYBYTES
 #define crypto_sign_SECRETKEYBYTES crypto_sign_ed25519_SECRETKEYBYTES
 #define crypto_sign_PRIMITIVE "ed25519"
diff --git a/src/libsodium/crypto_sign/ed25519/sign_ed25519_api.c b/src/libsodium/crypto_sign/ed25519/sign_ed25519_api.c
index a02031c9..8d2382c0 100644
--- a/src/libsodium/crypto_sign/ed25519/sign_ed25519_api.c
+++ b/src/libsodium/crypto_sign/ed25519/sign_ed25519_api.c
@@ -5,6 +5,11 @@ crypto_sign_ed25519_bytes(void) {
     return crypto_sign_ed25519_BYTES;
 }
 
+size_t
+crypto_sign_ed25519_seedbytes(void) {
+    return crypto_sign_ed25519_SEEDBYTES;
+}
+
 size_t
 crypto_sign_ed25519_publickeybytes(void) {
     return crypto_sign_ed25519_PUBLICKEYBYTES;
diff --git a/src/libsodium/include/sodium/crypto_sign.h b/src/libsodium/include/sodium/crypto_sign.h
index 60d37ae0..9efb2ebc 100644
--- a/src/libsodium/include/sodium/crypto_sign.h
+++ b/src/libsodium/include/sodium/crypto_sign.h
@@ -21,6 +21,10 @@ extern "C" {
 SODIUM_EXPORT
 size_t  crypto_sign_bytes(void);
 
+#define crypto_sign_SEEDBYTES crypto_sign_ed25519_SEEDBYTES
+SODIUM_EXPORT
+size_t  crypto_sign_seedbytes(void);
+
 #define crypto_sign_PUBLICKEYBYTES crypto_sign_ed25519_PUBLICKEYBYTES
 SODIUM_EXPORT
 size_t  crypto_sign_publickeybytes(void);
diff --git a/src/libsodium/include/sodium/crypto_sign_ed25519.h b/src/libsodium/include/sodium/crypto_sign_ed25519.h
index c572c6a7..aaf7082c 100644
--- a/src/libsodium/include/sodium/crypto_sign_ed25519.h
+++ b/src/libsodium/include/sodium/crypto_sign_ed25519.h
@@ -6,6 +6,7 @@
 
 #define crypto_sign_ed25519_SECRETKEYBYTES 64U
 #define crypto_sign_ed25519_PUBLICKEYBYTES 32U
+#define crypto_sign_ed25519_SEEDBYTES 32U
 #define crypto_sign_ed25519_BYTES 64U
 
 #ifdef __cplusplus
@@ -15,6 +16,9 @@ extern "C" {
 SODIUM_EXPORT
 size_t crypto_sign_ed25519_bytes(void);
 
+SODIUM_EXPORT
+size_t crypto_sign_ed25519_seedbytes(void);
+
 SODIUM_EXPORT
 size_t crypto_sign_ed25519_publickeybytes(void);