diff --git a/src/shrpx_client_handler.cc b/src/shrpx_client_handler.cc
index 25f2f0b6..750acee1 100644
--- a/src/shrpx_client_handler.cc
+++ b/src/shrpx_client_handler.cc
@@ -1171,7 +1171,7 @@ ClientHandler::get_downstream_connection(int &err, Downstream *downstream) {
     }
 
     dconn =
-        make_unique<HttpDownstreamConnection>(group, -1, conn_.loop, worker_);
+        make_unique<HttpDownstreamConnection>(group, 0, conn_.loop, worker_);
   }
 
   dconn->set_client_handler(this);
diff --git a/src/shrpx_http_downstream_connection.cc b/src/shrpx_http_downstream_connection.cc
index 3b26ef72..4fdcb643 100644
--- a/src/shrpx_http_downstream_connection.cc
+++ b/src/shrpx_http_downstream_connection.cc
@@ -182,7 +182,7 @@ void connectcb(struct ev_loop *loop, ev_io *w, int revents) {
 } // namespace
 
 HttpDownstreamConnection::HttpDownstreamConnection(
-    const std::shared_ptr<DownstreamAddrGroup> &group, ssize_t initial_addr_idx,
+    const std::shared_ptr<DownstreamAddrGroup> &group, size_t initial_addr_idx,
     struct ev_loop *loop, Worker *worker)
     : conn_(loop, -1, nullptr, worker->get_mcpool(),
             worker->get_downstream_config()->timeout.write,
diff --git a/src/shrpx_http_downstream_connection.h b/src/shrpx_http_downstream_connection.h
index 94178858..baea026c 100644
--- a/src/shrpx_http_downstream_connection.h
+++ b/src/shrpx_http_downstream_connection.h
@@ -44,7 +44,7 @@ struct DNSQuery;
 class HttpDownstreamConnection : public DownstreamConnection {
 public:
   HttpDownstreamConnection(const std::shared_ptr<DownstreamAddrGroup> &group,
-                           ssize_t initial_addr_idx, struct ev_loop *loop,
+                           size_t initial_addr_idx, struct ev_loop *loop,
                            Worker *worker);
   virtual ~HttpDownstreamConnection();
   virtual int attach_downstream(Downstream *downstream);
@@ -109,9 +109,8 @@ private:
   IOControl ioctrl_;
   http_parser response_htp_;
   // Index to backend address.  If client affinity is enabled, it is
-  // the index to affinity_hash.  Otherwise, it is the index to the
-  // backend addresses.
-  ssize_t initial_addr_idx_;
+  // the index to affinity_hash.  Otherwise, it is 0, and not used.
+  size_t initial_addr_idx_;
   // true if first write of reused connection succeeded.  For
   // convenience, this is initialized as true.
   bool reuse_first_write_done_;