diff --git a/src/libsodium/crypto_core/ed25519/core_ed25519.c b/src/libsodium/crypto_core/ed25519/core_ed25519.c
index 623ab3b1..3d5a8b34 100644
--- a/src/libsodium/crypto_core/ed25519/core_ed25519.c
+++ b/src/libsodium/crypto_core/ed25519/core_ed25519.c
@@ -92,6 +92,7 @@ _string_to_points(unsigned char * const px, size_t n,
     if (n > 2U) {
         abort(); /* LCOV_EXCL_LINE */
     }
+    COMPILER_ASSERT(2U * HASH_L <= 0xff);
     if (ctx_len > (size_t) 0xff) {
         crypto_hash_sha512_init(&st);
         crypto_hash_sha512_update(&st,