diff --git a/src/h2load.cc b/src/h2load.cc
index c9a36026..0658d623 100644
--- a/src/h2load.cc
+++ b/src/h2load.cc
@@ -198,7 +198,11 @@ namespace {
 void client_request_timeout_cb(struct ev_loop *loop, ev_timer *w, int revents) {
   auto client = static_cast<Client *>(w->data);
 
-  client->submit_request();
+  if (client->submit_request() != 0) {
+    ev_timer_stop(client->worker->loop, w);
+    client->process_request_failure();
+    return;
+  }
   client->signal_write();
 
   if (check_stop_client_request_timeout(client, w)) {
@@ -209,7 +213,11 @@ void client_request_timeout_cb(struct ev_loop *loop, ev_timer *w, int revents) {
       config.timings[client->reqidx] - config.timings[client->reqidx - 1];
 
   while (duration < 1e-9) {
-    client->submit_request();
+    if (client->submit_request() != 0) {
+      ev_timer_stop(client->worker->loop, w);
+      client->process_request_failure();
+      return;
+    }
     client->signal_write();
     if (check_stop_client_request_timeout(client, w)) {
       return;
@@ -388,9 +396,13 @@ void Client::disconnect() {
   }
 }
 
-void Client::submit_request() {
+int Client::submit_request() {
   auto req_stat = &worker->stats.req_stats[worker->stats.req_started++];
-  session->submit_request(req_stat);
+
+  if (session->submit_request(req_stat) != 0) {
+    return -1;
+  }
+
   ++req_started;
 
   // if an active timeout is set and this is the last request to be submitted
@@ -398,6 +410,8 @@ void Client::submit_request() {
   if (worker->config->conn_active_timeout > 0. && req_started >= req_todo) {
     ev_timer_start(worker->loop, &conn_active_watcher);
   }
+
+  return 0;
 }
 
 void Client::process_timedout_streams() {
@@ -423,6 +437,21 @@ void Client::process_abandoned_streams() {
   req_done = req_todo;
 }
 
+void Client::process_request_failure() {
+  auto req_abandoned = req_todo - req_started;
+
+  worker->stats.req_failed += req_abandoned;
+  worker->stats.req_error += req_abandoned;
+  worker->stats.req_done += req_abandoned;
+
+  req_done += req_abandoned;
+
+  if (req_done == req_todo) {
+    terminate_session();
+    return;
+  }
+}
+
 void Client::report_progress() {
   if (!worker->config->is_rate_mode() && worker->id == 0 &&
       worker->stats.req_done % worker->progress_interval == 0) {
@@ -488,7 +517,11 @@ void Client::report_app_info() {
   }
 }
 
-void Client::terminate_session() { session->terminate(); }
+void Client::terminate_session() {
+  session->terminate();
+  // http1 session needs writecb to tear down session.
+  signal_write();
+}
 
 void Client::on_request(int32_t stream_id) { streams[stream_id] = Stream(); }
 
@@ -579,7 +612,9 @@ void Client::on_stream_close(int32_t stream_id, bool success,
 
   if (!config.timing_script && !final) {
     if (req_started < req_todo) {
-      submit_request();
+      if (submit_request() != 0) {
+        process_request_failure();
+      }
       return;
     }
   }
@@ -692,14 +727,20 @@ int Client::connection_made() {
         std::min(req_todo - req_started, (size_t)config.max_concurrent_streams);
 
     for (; nreq > 0; --nreq) {
-      submit_request();
+      if (submit_request() != 0) {
+        process_request_failure();
+        break;
+      }
     }
   } else {
 
     ev_tstamp duration = config.timings[reqidx];
 
     while (duration < 1e-9) {
-      submit_request();
+      if (submit_request() != 0) {
+        process_request_failure();
+        break;
+      }
       duration = config.timings[reqidx];
     }
 
diff --git a/src/h2load.h b/src/h2load.h
index 577b8158..0b5f747b 100644
--- a/src/h2load.h
+++ b/src/h2load.h
@@ -260,7 +260,8 @@ struct Client {
   void fail();
   void timeout();
   void restart_timeout();
-  void submit_request();
+  int submit_request();
+  void process_request_failure();
   void process_timedout_streams();
   void process_abandoned_streams();
   void report_progress();
diff --git a/src/h2load_http1_session.cc b/src/h2load_http1_session.cc
index b354db07..30691ed8 100644
--- a/src/h2load_http1_session.cc
+++ b/src/h2load_http1_session.cc
@@ -140,7 +140,7 @@ http_parser_settings htp_hooks = {
 
 void Http1Session::on_connect() { client_->signal_write(); }
 
-void Http1Session::submit_request(RequestStat *req_stat) {
+int Http1Session::submit_request(RequestStat *req_stat) {
   auto config = client_->worker->config;
   auto req = config->h1reqs[client_->reqidx];
   client_->reqidx++;
@@ -158,6 +158,8 @@ void Http1Session::submit_request(RequestStat *req_stat) {
 
   // increment for next request
   stream_req_counter_ += 2;
+
+  return 0;
 }
 
 int Http1Session::on_read(const uint8_t *data, size_t len) {
diff --git a/src/h2load_http1_session.h b/src/h2load_http1_session.h
index bb0600eb..a19ba65e 100644
--- a/src/h2load_http1_session.h
+++ b/src/h2load_http1_session.h
@@ -38,7 +38,7 @@ public:
   Http1Session(Client *client);
   virtual ~Http1Session();
   virtual void on_connect();
-  virtual void submit_request(RequestStat *req_stat);
+  virtual int submit_request(RequestStat *req_stat);
   virtual int on_read(const uint8_t *data, size_t len);
   virtual int on_write();
   virtual void terminate();
diff --git a/src/h2load_http2_session.cc b/src/h2load_http2_session.cc
index 2b56d115..86045240 100644
--- a/src/h2load_http2_session.cc
+++ b/src/h2load_http2_session.cc
@@ -209,7 +209,7 @@ void Http2Session::on_connect() {
   client_->signal_write();
 }
 
-void Http2Session::submit_request(RequestStat *req_stat) {
+int Http2Session::submit_request(RequestStat *req_stat) {
   auto config = client_->worker->config;
   auto &nva = config->nva[client_->reqidx++];
 
@@ -222,7 +222,11 @@ void Http2Session::submit_request(RequestStat *req_stat) {
   auto stream_id =
       nghttp2_submit_request(session_, nullptr, nva.data(), nva.size(),
                              config->data_fd == -1 ? nullptr : &prd, req_stat);
-  assert(stream_id > 0);
+  if (stream_id < 0) {
+    return -1;
+  }
+
+  return 0;
 }
 
 int Http2Session::on_read(const uint8_t *data, size_t len) {
diff --git a/src/h2load_http2_session.h b/src/h2load_http2_session.h
index a06e4118..c3a3344b 100644
--- a/src/h2load_http2_session.h
+++ b/src/h2load_http2_session.h
@@ -38,7 +38,7 @@ public:
   Http2Session(Client *client);
   virtual ~Http2Session();
   virtual void on_connect();
-  virtual void submit_request(RequestStat *req_stat);
+  virtual int submit_request(RequestStat *req_stat);
   virtual int on_read(const uint8_t *data, size_t len);
   virtual int on_write();
   virtual void terminate();
diff --git a/src/h2load_session.h b/src/h2load_session.h
index 18175748..1f8ed60a 100644
--- a/src/h2load_session.h
+++ b/src/h2load_session.h
@@ -41,7 +41,7 @@ public:
   // Called when the connection was made.
   virtual void on_connect() = 0;
   // Called when one request must be issued.
-  virtual void submit_request(RequestStat *req_stat) = 0;
+  virtual int submit_request(RequestStat *req_stat) = 0;
   // Called when incoming bytes are available. The subclass has to
   // return the number of bytes read.
   virtual int on_read(const uint8_t *data, size_t len) = 0;
diff --git a/src/h2load_spdy_session.cc b/src/h2load_spdy_session.cc
index 9700a518..a7d52de7 100644
--- a/src/h2load_spdy_session.cc
+++ b/src/h2load_spdy_session.cc
@@ -178,7 +178,8 @@ void SpdySession::on_connect() {
   client_->signal_write();
 }
 
-void SpdySession::submit_request(RequestStat *req_stat) {
+int SpdySession::submit_request(RequestStat *req_stat) {
+  int rv;
   auto config = client_->worker->config;
   auto &nv = config->nv[client_->reqidx++];
 
@@ -188,8 +189,14 @@ void SpdySession::submit_request(RequestStat *req_stat) {
 
   spdylay_data_provider prd{{0}, file_read_callback};
 
-  spdylay_submit_request(session_, 0, nv.data(),
-                         config->data_fd == -1 ? nullptr : &prd, req_stat);
+  rv = spdylay_submit_request(session_, 0, nv.data(),
+                              config->data_fd == -1 ? nullptr : &prd, req_stat);
+
+  if (rv != 0) {
+    return -1;
+  }
+
+  return 0;
 }
 
 int SpdySession::on_read(const uint8_t *data, size_t len) {
diff --git a/src/h2load_spdy_session.h b/src/h2load_spdy_session.h
index f76f25ac..288be1df 100644
--- a/src/h2load_spdy_session.h
+++ b/src/h2load_spdy_session.h
@@ -40,7 +40,7 @@ public:
   SpdySession(Client *client, uint16_t spdy_version);
   virtual ~SpdySession();
   virtual void on_connect();
-  virtual void submit_request(RequestStat *req_stat);
+  virtual int submit_request(RequestStat *req_stat);
   virtual int on_read(const uint8_t *data, size_t len);
   virtual int on_write();
   virtual void terminate();