diff --git a/src/shrpx.cc b/src/shrpx.cc
index 959c15bf..f6847bd3 100644
--- a/src/shrpx.cc
+++ b/src/shrpx.cc
@@ -1109,8 +1109,8 @@ void fill_default_config() {
 
     // For API endpoint, we enable automatic window update.  This is
     // because we are a sink.
-    nghttp2_option_new(&upstreamconf.api_option);
-    nghttp2_option_set_no_recv_client_magic(upstreamconf.api_option, 1);
+    nghttp2_option_new(&upstreamconf.alt_mode_option);
+    nghttp2_option_set_no_recv_client_magic(upstreamconf.alt_mode_option, 1);
   }
 
   {
diff --git a/src/shrpx_client_handler.cc b/src/shrpx_client_handler.cc
index d1e4c25d..9ba99b9b 100644
--- a/src/shrpx_client_handler.cc
+++ b/src/shrpx_client_handler.cc
@@ -896,7 +896,8 @@ ClientHandler::get_downstream_connection(Downstream *downstream) {
 
   const auto &req = downstream->request();
 
-  if (faddr_->api) {
+  switch (faddr_->alt_mode) {
+  case ALTMODE_API:
     return make_unique<APIDownstreamConnection>(worker_);
   }
 
diff --git a/src/shrpx_config.cc b/src/shrpx_config.cc
index 6a9e5271..21f81232 100644
--- a/src/shrpx_config.cc
+++ b/src/shrpx_config.cc
@@ -610,8 +610,8 @@ int parse_memcached_connection_params(MemcachedConnectionParams &out,
 } // namespace
 
 struct UpstreamParams {
+  int alt_mode;
   bool tls;
-  bool api;
 };
 
 namespace {
@@ -629,7 +629,7 @@ int parse_upstream_params(UpstreamParams &out, const StringRef &src_params) {
     } else if (util::strieq_l("no-tls", param)) {
       out.tls = false;
     } else if (util::strieq_l("api", param)) {
-      out.api = true;
+      out.alt_mode = ALTMODE_API;
     } else if (!param.empty()) {
       LOG(ERROR) << "frontend: " << param << ": unknown keyword";
       return -1;
@@ -1736,9 +1736,9 @@ int parse_config(Config *config, int optid, const StringRef &opt,
     UpstreamAddr addr{};
     addr.fd = -1;
     addr.tls = params.tls;
-    addr.api = params.api;
+    addr.alt_mode = params.alt_mode;
 
-    if (addr.api) {
+    if (addr.alt_mode == ALTMODE_API) {
       listenerconf.api = true;
     }
 
diff --git a/src/shrpx_config.h b/src/shrpx_config.h
index aa9522ac..347aa0b1 100644
--- a/src/shrpx_config.h
+++ b/src/shrpx_config.h
@@ -316,6 +316,13 @@ struct AltSvc {
   uint16_t port;
 };
 
+enum UpstreamAltMode {
+  // No alternative mode
+  ALTMODE_NONE,
+  // API processing mode
+  ALTMODE_API,
+};
+
 struct UpstreamAddr {
   // The frontend address (e.g., FQDN, hostname, IP address).  If
   // |host_unix| is true, this is UNIX domain socket path.
@@ -329,12 +336,12 @@ struct UpstreamAddr {
   // For TCP socket, this is either AF_INET or AF_INET6.  For UNIX
   // domain socket, this is 0.
   int family;
+  // Alternate mode
+  int alt_mode;
   // true if |host| contains UNIX domain socket path.
   bool host_unix;
   // true if TLS is enabled.
   bool tls;
-  // true if this is an API endpoint.
-  bool api;
   int fd;
 };
 
@@ -554,7 +561,7 @@ struct Http2Config {
       ev_tstamp settings;
     } timeout;
     nghttp2_option *option;
-    nghttp2_option *api_option;
+    nghttp2_option *alt_mode_option;
     nghttp2_session_callbacks *callbacks;
     size_t window_bits;
     size_t connection_window_bits;
diff --git a/src/shrpx_connection_handler.cc b/src/shrpx_connection_handler.cc
index bc76ad47..87f03221 100644
--- a/src/shrpx_connection_handler.cc
+++ b/src/shrpx_connection_handler.cc
@@ -393,7 +393,7 @@ int ConnectionHandler::handle_connection(int fd, sockaddr *addr, int addrlen,
 
   Worker *worker;
 
-  if (faddr->api) {
+  if (faddr->alt_mode == ALTMODE_API) {
     worker = workers_[0].get();
 
     if (LOG_ENABLED(INFO)) {
diff --git a/src/shrpx_downstream.cc b/src/shrpx_downstream.cc
index 60ac686d..8afd7fc4 100644
--- a/src/shrpx_downstream.cc
+++ b/src/shrpx_downstream.cc
@@ -505,7 +505,7 @@ bool Downstream::request_buf_full() {
   auto worker = handler->get_worker();
 
   // We don't check buffer size here for API endpoint.
-  if (faddr->api) {
+  if (faddr->alt_mode == ALTMODE_API) {
     return false;
   }
 
diff --git a/src/shrpx_http2_upstream.cc b/src/shrpx_http2_upstream.cc
index 28647631..518335bb 100644
--- a/src/shrpx_http2_upstream.cc
+++ b/src/shrpx_http2_upstream.cc
@@ -879,7 +879,8 @@ Http2Upstream::Http2Upstream(ClientHandler *handler)
 
   rv = nghttp2_session_server_new2(
       &session_, http2conf.upstream.callbacks, this,
-      faddr->api ? http2conf.upstream.api_option : http2conf.upstream.option);
+      faddr->alt_mode ? http2conf.upstream.alt_mode_option
+                      : http2conf.upstream.option);
 
   assert(rv == 0);
 
@@ -891,7 +892,7 @@ Http2Upstream::Http2Upstream(ClientHandler *handler)
   entry[0].value = http2conf.upstream.max_concurrent_streams;
 
   entry[1].settings_id = NGHTTP2_SETTINGS_INITIAL_WINDOW_SIZE;
-  if (faddr->api) {
+  if (faddr->alt_mode) {
     entry[1].value = (1u << 31) - 1;
   } else {
     entry[1].value = (1 << http2conf.upstream.window_bits) - 1;
@@ -905,7 +906,7 @@ Http2Upstream::Http2Upstream(ClientHandler *handler)
   }
 
   int32_t window_bits =
-      faddr->api ? 31 : http2conf.upstream.connection_window_bits;
+      faddr->alt_mode ? 31 : http2conf.upstream.connection_window_bits;
 
   if (window_bits != 16) {
     int32_t window_size = (1u << window_bits) - 1;
@@ -1701,7 +1702,7 @@ int Http2Upstream::consume(int32_t stream_id, size_t len) {
 
   auto faddr = handler_->get_upstream_addr();
 
-  if (faddr->api) {
+  if (faddr->alt_mode) {
     return 0;
   }
 
diff --git a/src/shrpx_https_upstream.cc b/src/shrpx_https_upstream.cc
index 24c80c7d..1f5e4640 100644
--- a/src/shrpx_https_upstream.cc
+++ b/src/shrpx_https_upstream.cc
@@ -413,11 +413,11 @@ int htp_hdrs_completecb(http_parser *htp) {
 
   auto faddr = handler->get_upstream_addr();
 
-  if (faddr->api) {
+  if (faddr->alt_mode) {
     // Normally, we forward expect: 100-continue to backend server,
     // and let them decide whether responds with 100 Continue or not.
-    // For API endpoint, we have no backend, so just send 100 Continue
-    // here to make the client happy.
+    // For alternative mode, we have no backend, so just send 100
+    // Continue here to make the client happy.
     auto expect = req.fs.header(http2::HD_EXPECT);
     if (expect &&
         util::strieq(expect->value, StringRef::from_lit("100-continue"))) {
diff --git a/src/shrpx_spdy_upstream.cc b/src/shrpx_spdy_upstream.cc
index df78b9c0..0d09fccc 100644
--- a/src/shrpx_spdy_upstream.cc
+++ b/src/shrpx_spdy_upstream.cc
@@ -565,7 +565,7 @@ SpdyUpstream::SpdyUpstream(uint16_t version, ClientHandler *handler)
   // going to be deprecated in the future, and the default stream
   // window is large enough for API request body (64KiB), we don't
   // expand window size depending on the options.
-  if (version >= SPDYLAY_PROTO_SPDY3 && !faddr->api) {
+  if (version >= SPDYLAY_PROTO_SPDY3 && !faddr->alt_mode) {
     int val = 1;
     flow_control_ = true;
     initial_window_size_ = 1 << http2conf.upstream.window_bits;