diff --git a/src/libsodium/include/sodium/crypto_aead_xchacha20poly1305.h b/src/libsodium/include/sodium/crypto_aead_xchacha20poly1305.h
index a13b2247..6643b0cb 100644
--- a/src/libsodium/include/sodium/crypto_aead_xchacha20poly1305.h
+++ b/src/libsodium/include/sodium/crypto_aead_xchacha20poly1305.h
@@ -79,7 +79,7 @@ int crypto_aead_xchacha20poly1305_ietf_decrypt_detached(unsigned char *m,
                                                         unsigned long long adlen,
                                                         const unsigned char *npub,
                                                         const unsigned char *k)
-            __attribute__ ((warn_unused_result)) __attribute__ ((nonnull(3, 5, 9, 9)));
+            __attribute__ ((warn_unused_result)) __attribute__ ((nonnull(3, 5, 8, 9)));
 
 SODIUM_EXPORT
 void crypto_aead_xchacha20poly1305_ietf_keygen(unsigned char k[crypto_aead_xchacha20poly1305_ietf_KEYBYTES])