diff --git a/src/libsodium/crypto_aead/chacha20poly1305/sodium/aead_chacha20poly1305.c b/src/libsodium/crypto_aead/chacha20poly1305/sodium/aead_chacha20poly1305.c
index e9d902e6..b5dbd71f 100644
--- a/src/libsodium/crypto_aead/chacha20poly1305/sodium/aead_chacha20poly1305.c
+++ b/src/libsodium/crypto_aead/chacha20poly1305/sodium/aead_chacha20poly1305.c
@@ -107,6 +107,7 @@ crypto_aead_chacha20poly1305_decrypt(unsigned char *m,
     crypto_onetimeauth_poly1305_final(&state, mac);
     sodium_memzero(&state, sizeof state);
 
+    (void) sizeof(int[sizeof mac == 16U ? 1 : -1]);
     ret = crypto_verify_16(mac,
                            c + clen - crypto_aead_chacha20poly1305_ABYTES);
     sodium_memzero(mac, sizeof mac);