diff --git a/src/libsodium/crypto_sign/ed25519/ref10/sign.c b/src/libsodium/crypto_sign/ed25519/ref10/sign.c
index 604bad9b..c56367df 100644
--- a/src/libsodium/crypto_sign/ed25519/ref10/sign.c
+++ b/src/libsodium/crypto_sign/ed25519/ref10/sign.c
@@ -45,6 +45,7 @@ crypto_sign_detached(unsigned char *sig, unsigned long long *siglen,
     sc_reduce(hram);
     sc_muladd(sig + 32, hram, az, nonce);
 
+    sodium_memzero(az, sizeof az);
     sodium_memzero(nonce, sizeof nonce);
 
     if (siglen != NULL) {