diff --git a/examples/client.c b/examples/client.c
index 3ddeafe4..5d210a28 100644
--- a/examples/client.c
+++ b/examples/client.c
@@ -379,7 +379,7 @@ static void init_ssl_ctx(SSL_CTX *ssl_ctx) {
   /* Set NPN callback */
 #ifndef OPENSSL_NO_NEXTPROTONEG
   SSL_CTX_set_next_proto_select_cb(ssl_ctx, select_next_proto_cb, NULL);
-#endif
+#endif /* !OPENSSL_NO_NEXTPROTONEG */
 }
 
 static void ssl_handshake(SSL *ssl, int fd) {
diff --git a/examples/libevent-client.c b/examples/libevent-client.c
index f297df4f..f998fba3 100644
--- a/examples/libevent-client.c
+++ b/examples/libevent-client.c
@@ -339,7 +339,7 @@ static SSL_CTX *create_ssl_ctx(void) {
                           SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION);
 #ifndef OPENSSL_NO_NEXTPROTONEG
   SSL_CTX_set_next_proto_select_cb(ssl_ctx, select_next_proto_cb, NULL);
-#endif
+#endif /* !OPENSSL_NO_NEXTPROTONEG */
 
 #if OPENSSL_VERSION_NUMBER >= 0x10002000L
   SSL_CTX_set_alpn_protos(ssl_ctx, (const unsigned char *)"\x02h2", 3);
@@ -510,7 +510,7 @@ static void eventcb(struct bufferevent *bev, short events, void *ptr) {
 
 #ifndef OPENSSL_NO_NEXTPROTONEG
     SSL_get0_next_proto_negotiated(ssl, &alpn, &alpnlen);
-#endif
+#endif /* !OPENSSL_NO_NEXTPROTONEG */
 #if OPENSSL_VERSION_NUMBER >= 0x10002000L
     if (alpn == NULL) {
       SSL_get0_alpn_selected(ssl, &alpn, &alpnlen);
diff --git a/examples/libevent-server.c b/examples/libevent-server.c
index 59091c54..06b36b9a 100644
--- a/examples/libevent-server.c
+++ b/examples/libevent-server.c
@@ -176,7 +176,7 @@ static SSL_CTX *create_ssl_ctx(const char *key_file, const char *cert_file) {
 
 #ifndef OPENSSL_NO_NEXTPROTONEG
   SSL_CTX_set_next_protos_advertised_cb(ssl_ctx, next_proto_cb, NULL);
-#endif
+#endif /* !OPENSSL_NO_NEXTPROTONEG */
 
 #if OPENSSL_VERSION_NUMBER >= 0x10002000L
   SSL_CTX_set_alpn_select_cb(ssl_ctx, alpn_select_proto_cb, NULL);
@@ -696,7 +696,7 @@ static void eventcb(struct bufferevent *bev, short events, void *ptr) {
 
 #ifndef OPENSSL_NO_NEXTPROTONEG
     SSL_get0_next_proto_negotiated(ssl, &alpn, &alpnlen);
-#endif
+#endif /* !OPENSSL_NO_NEXTPROTONEG */
 #if OPENSSL_VERSION_NUMBER >= 0x10002000L
     if (alpn == NULL) {
       SSL_get0_alpn_selected(ssl, &alpn, &alpnlen);
diff --git a/src/HttpServer.cc b/src/HttpServer.cc
index 72d61b19..a6afa0c4 100644
--- a/src/HttpServer.cc
+++ b/src/HttpServer.cc
@@ -890,7 +890,7 @@ int Http2Handler::verify_npn_result() {
   // Check the negotiated protocol in NPN or ALPN
 #ifndef OPENSSL_NO_NEXTPROTONEG
   SSL_get0_next_proto_negotiated(ssl_, &next_proto, &next_proto_len);
-#endif
+#endif // !OPENSSL_NO_NEXTPROTONEG
   for (int i = 0; i < 2; ++i) {
     if (next_proto) {
       auto proto = StringRef{next_proto, next_proto_len};
@@ -2211,7 +2211,7 @@ int HttpServer::run() {
 
 #ifndef OPENSSL_NO_NEXTPROTONEG
     SSL_CTX_set_next_protos_advertised_cb(ssl_ctx, next_proto_cb, &next_proto);
-#endif
+#endif // !OPENSSL_NO_NEXTPROTONEG
 #if OPENSSL_VERSION_NUMBER >= 0x10002000L
     // ALPN selection callback
     SSL_CTX_set_alpn_select_cb(ssl_ctx, alpn_select_proto_cb, this);
diff --git a/src/asio_common.cc b/src/asio_common.cc
index 6aa46abc..90762d3d 100644
--- a/src/asio_common.cc
+++ b/src/asio_common.cc
@@ -179,7 +179,7 @@ bool tls_h2_negotiated(ssl_socket &socket) {
 
 #ifndef OPENSSL_NO_NEXTPROTONEG
   SSL_get0_next_proto_negotiated(ssl, &next_proto, &next_proto_len);
-#endif
+#endif // !OPENSSL_NO_NEXTPROTONEG
 #if OPENSSL_VERSION_NUMBER >= 0x10002000L
   if (next_proto == nullptr) {
     SSL_get0_alpn_selected(ssl, &next_proto, &next_proto_len);
diff --git a/src/h2load.cc b/src/h2load.cc
index 253a07c8..8dee4ffb 100644
--- a/src/h2load.cc
+++ b/src/h2load.cc
@@ -859,7 +859,7 @@ int Client::connection_made() {
 
 #ifndef OPENSSL_NO_NEXTPROTONEG
     SSL_get0_next_proto_negotiated(ssl, &next_proto, &next_proto_len);
-#endif
+#endif // !OPENSSL_NO_NEXTPROTONEG
 #if OPENSSL_VERSION_NUMBER >= 0x10002000L
     if (next_proto == nullptr) {
       SSL_get0_alpn_selected(ssl, &next_proto, &next_proto_len);
@@ -2406,7 +2406,7 @@ int main(int argc, char **argv) {
 #ifndef OPENSSL_NO_NEXTPROTONEG
   SSL_CTX_set_next_proto_select_cb(ssl_ctx, client_select_next_proto_cb,
                                    nullptr);
-#endif
+#endif // !OPENSSL_NO_NEXTPROTONEG
 
 #if OPENSSL_VERSION_NUMBER >= 0x10002000L
   std::vector<unsigned char> proto_list;
diff --git a/src/nghttp.cc b/src/nghttp.cc
index bddccec3..ca4a02a4 100644
--- a/src/nghttp.cc
+++ b/src/nghttp.cc
@@ -1097,7 +1097,7 @@ int HttpClient::connection_made() {
     unsigned int next_proto_len;
 #ifndef OPENSSL_NO_NEXTPROTONEG
     SSL_get0_next_proto_negotiated(ssl, &next_proto, &next_proto_len);
-#endif
+#endif // !OPENSSL_NO_NEXTPROTONEG
     for (int i = 0; i < 2; ++i) {
       if (next_proto) {
         auto proto = StringRef{next_proto, next_proto_len};
@@ -2315,7 +2315,7 @@ int communicate(
 #ifndef OPENSSL_NO_NEXTPROTONEG
     SSL_CTX_set_next_proto_select_cb(ssl_ctx, client_select_next_proto_cb,
                                      nullptr);
-#endif
+#endif // !OPENSSL_NO_NEXTPROTONEG
 
 #if OPENSSL_VERSION_NUMBER >= 0x10002000L
     auto proto_list = util::get_default_alpn();
diff --git a/src/shrpx_client_handler.cc b/src/shrpx_client_handler.cc
index 491b2e35..941e0e12 100644
--- a/src/shrpx_client_handler.cc
+++ b/src/shrpx_client_handler.cc
@@ -551,7 +551,7 @@ int ClientHandler::validate_next_proto() {
 
 #ifndef OPENSSL_NO_NEXTPROTONEG
   SSL_get0_next_proto_negotiated(conn_.tls.ssl, &next_proto, &next_proto_len);
-#endif
+#endif // !OPENSSL_NO_NEXTPROTONEG
 #if OPENSSL_VERSION_NUMBER >= 0x10002000L
   if (next_proto == nullptr) {
     SSL_get0_alpn_selected(conn_.tls.ssl, &next_proto, &next_proto_len);
diff --git a/src/shrpx_connection.cc b/src/shrpx_connection.cc
index 3ea37b5a..31dac3c6 100644
--- a/src/shrpx_connection.cc
+++ b/src/shrpx_connection.cc
@@ -525,7 +525,7 @@ int Connection::check_http2_requirement() {
 
 #ifndef OPENSSL_NO_NEXTPROTONEG
   SSL_get0_next_proto_negotiated(tls.ssl, &next_proto, &next_proto_len);
-#endif
+#endif // !OPENSSL_NO_NEXTPROTONEG
 #if OPENSSL_VERSION_NUMBER >= 0x10002000L
   if (next_proto == nullptr) {
     SSL_get0_alpn_selected(tls.ssl, &next_proto, &next_proto_len);
diff --git a/src/shrpx_http2_session.cc b/src/shrpx_http2_session.cc
index c2deae04..67039867 100644
--- a/src/shrpx_http2_session.cc
+++ b/src/shrpx_http2_session.cc
@@ -1651,7 +1651,7 @@ int Http2Session::connection_made() {
 
 #ifndef OPENSSL_NO_NEXTPROTONEG
     SSL_get0_next_proto_negotiated(conn_.tls.ssl, &next_proto, &next_proto_len);
-#endif
+#endif // !OPENSSL_NO_NEXTPROTONEG
 #if OPENSSL_VERSION_NUMBER >= 0x10002000L
     if (!next_proto) {
       SSL_get0_alpn_selected(conn_.tls.ssl, &next_proto, &next_proto_len);
diff --git a/src/shrpx_live_check.cc b/src/shrpx_live_check.cc
index 07ad811e..9d30ca78 100644
--- a/src/shrpx_live_check.cc
+++ b/src/shrpx_live_check.cc
@@ -408,7 +408,7 @@ int LiveCheck::tls_handshake() {
 
 #ifndef OPENSSL_NO_NEXTPROTONEG
   SSL_get0_next_proto_negotiated(conn_.tls.ssl, &next_proto, &next_proto_len);
-#endif
+#endif // !OPENSSL_NO_NEXTPROTONEG
 #if OPENSSL_VERSION_NUMBER >= 0x10002000L
   if (next_proto == nullptr) {
     SSL_get0_alpn_selected(conn_.tls.ssl, &next_proto, &next_proto_len);
diff --git a/src/shrpx_tls.cc b/src/shrpx_tls.cc
index 6dbd456c..784de58d 100644
--- a/src/shrpx_tls.cc
+++ b/src/shrpx_tls.cc
@@ -927,7 +927,7 @@ SSL_CTX *create_ssl_context(const char *private_key_file, const char *cert_file,
   // NPN advertisement
 #ifndef OPENSSL_NO_NEXTPROTONEG
   SSL_CTX_set_next_protos_advertised_cb(ssl_ctx, next_proto_cb, nullptr);
-#endif
+#endif // !OPENSSL_NO_NEXTPROTONEG
 #if OPENSSL_VERSION_NUMBER >= 0x10002000L
   // ALPN selection callback
   SSL_CTX_set_alpn_select_cb(ssl_ctx, alpn_select_proto_cb, nullptr);
@@ -1124,7 +1124,7 @@ SSL_CTX *create_ssl_client_context(
   // OpenSSL does not offer SSL_set_next_proto_select_cb.
 #ifndef OPENSSL_NO_NEXTPROTONEG
   SSL_CTX_set_next_proto_select_cb(ssl_ctx, next_proto_select_cb, nullptr);
-#endif
+#endif // !OPENSSL_NO_NEXTPROTONEG
 
   return ssl_ctx;
 }