diff --git a/src/libsodium/crypto_sign/ed25519/ref10/open.c b/src/libsodium/crypto_sign/ed25519/ref10/open.c
index 5e1280bd..3631edaf 100644
--- a/src/libsodium/crypto_sign/ed25519/ref10/open.c
+++ b/src/libsodium/crypto_sign/ed25519/ref10/open.c
@@ -28,7 +28,7 @@ _crypto_sign_ed25519_verify_detached(const unsigned char *sig,
         return -1;
     }
 #else
-    if ((sig[63] & 240) &&
+    if ((sig[63] & 240) != 0 &&
         sc25519_is_canonical(sig + 32) == 0) {
         return -1;
     }