diff --git a/lib/openssl.c b/lib/openssl.c
index 80613bb..49f6f51 100644
--- a/lib/openssl.c
+++ b/lib/openssl.c
@@ -1383,7 +1383,7 @@
 {
     ptls_openssl_raw_pubkey_verify_certificate_t *self = (ptls_openssl_raw_pubkey_verify_certificate_t *)_self;
     int ret = PTLS_ALERT_BAD_CERTIFICATE;
-    ptls_iovec_t expected_pubkey = {};
+    ptls_iovec_t expected_pubkey = { 0 };
 
     assert(num_certs != 0);