diff --git a/src/memchunk.h b/src/memchunk.h
index d2e7a6c7..0f12c15e 100644
--- a/src/memchunk.h
+++ b/src/memchunk.h
@@ -102,6 +102,11 @@ template <typename T> struct Pool {
     }
     freelist = m;
   }
+  void clear() {
+    freelist = nullptr;
+    pool = nullptr;
+    poolsize = 0;
+  }
   using value_type = T;
   std::unique_ptr<T> pool;
   T *freelist;
diff --git a/src/shrpx_client_handler.cc b/src/shrpx_client_handler.cc
index b397adf3..0a6457a4 100644
--- a/src/shrpx_client_handler.cc
+++ b/src/shrpx_client_handler.cc
@@ -404,6 +404,10 @@ ClientHandler::~ClientHandler() {
   auto worker_stat = worker_->get_worker_stat();
   --worker_stat->num_connections;
 
+  if (worker_stat->num_connections == 0) {
+    worker_->get_mcpool()->clear();
+  }
+
   ev_timer_stop(conn_.loop, &reneg_shutdown_timer_);
 
   // TODO If backend is http/2, and it is in CONNECTED state, signal
@@ -634,6 +638,8 @@ ClientHandler::get_downstream_connection() {
   return dconn;
 }
 
+MemchunkPool *ClientHandler::get_mcpool() { return worker_->get_mcpool(); }
+
 SSL *ClientHandler::get_ssl() const { return conn_.tls.ssl; }
 
 ConnectBlocker *ClientHandler::get_connect_blocker() const {
diff --git a/src/shrpx_client_handler.h b/src/shrpx_client_handler.h
index 88d11675..4367c2b5 100644
--- a/src/shrpx_client_handler.h
+++ b/src/shrpx_client_handler.h
@@ -36,6 +36,7 @@
 #include "shrpx_rate_limit.h"
 #include "shrpx_connection.h"
 #include "buffer.h"
+#include "memchunk.h"
 
 using namespace nghttp2;
 
@@ -92,6 +93,7 @@ public:
   void pool_downstream_connection(std::unique_ptr<DownstreamConnection> dconn);
   void remove_downstream_connection(DownstreamConnection *dconn);
   std::unique_ptr<DownstreamConnection> get_downstream_connection();
+  MemchunkPool *get_mcpool();
   SSL *get_ssl() const;
   ConnectBlocker *get_connect_blocker() const;
   // Call this function when HTTP/2 connection header is received at
diff --git a/src/shrpx_downstream.cc b/src/shrpx_downstream.cc
index a176de3e..87e8ff58 100644
--- a/src/shrpx_downstream.cc
+++ b/src/shrpx_downstream.cc
@@ -106,12 +106,12 @@ void downstream_wtimeoutcb(struct ev_loop *loop, ev_timer *w, int revents) {
 } // namespace
 
 // upstream could be nullptr for unittests
-Downstream::Downstream(Upstream *upstream, int32_t stream_id, int32_t priority)
+Downstream::Downstream(Upstream *upstream, MemchunkPool *mcpool,
+                       int32_t stream_id, int32_t priority)
     : dlnext(nullptr), dlprev(nullptr),
       request_start_time_(std::chrono::high_resolution_clock::now()),
-      request_buf_(upstream ? upstream->get_mcpool() : nullptr),
-      response_buf_(upstream ? upstream->get_mcpool() : nullptr),
-      request_bodylen_(0), response_bodylen_(0), response_sent_bodylen_(0),
+      request_buf_(mcpool), response_buf_(mcpool), request_bodylen_(0),
+      response_bodylen_(0), response_sent_bodylen_(0),
       request_content_length_(-1), response_content_length_(-1),
       upstream_(upstream), blocked_link_(nullptr), request_headers_sum_(0),
       response_headers_sum_(0), request_datalen_(0), response_datalen_(0),
diff --git a/src/shrpx_downstream.h b/src/shrpx_downstream.h
index 6febe806..1f55cd40 100644
--- a/src/shrpx_downstream.h
+++ b/src/shrpx_downstream.h
@@ -52,7 +52,8 @@ struct BlockedLink;
 
 class Downstream {
 public:
-  Downstream(Upstream *upstream, int32_t stream_id, int32_t priority);
+  Downstream(Upstream *upstream, MemchunkPool *mcpool, int32_t stream_id,
+             int32_t priority);
   ~Downstream();
   void reset_upstream(Upstream *upstream);
   Upstream *get_upstream() const;
diff --git a/src/shrpx_downstream_test.cc b/src/shrpx_downstream_test.cc
index ad0abaa4..2e7a6960 100644
--- a/src/shrpx_downstream_test.cc
+++ b/src/shrpx_downstream_test.cc
@@ -33,7 +33,7 @@
 namespace shrpx {
 
 void test_downstream_index_request_headers(void) {
-  Downstream d(nullptr, 0, 0);
+  Downstream d(nullptr, nullptr, 0, 0);
   d.add_request_header("1", "0");
   d.add_request_header("2", "1");
   d.add_request_header("Charlie", "2");
@@ -56,7 +56,7 @@ void test_downstream_index_request_headers(void) {
 }
 
 void test_downstream_index_response_headers(void) {
-  Downstream d(nullptr, 0, 0);
+  Downstream d(nullptr, nullptr, 0, 0);
   d.add_response_header("Charlie", "0");
   d.add_response_header("Alpha", "1");
   d.add_response_header("Delta", "2");
@@ -69,7 +69,7 @@ void test_downstream_index_response_headers(void) {
 }
 
 void test_downstream_get_request_header(void) {
-  Downstream d(nullptr, 0, 0);
+  Downstream d(nullptr, nullptr, 0, 0);
   d.add_request_header("alpha", "0");
   d.add_request_header(":authority", "1");
   d.add_request_header("content-length", "2");
@@ -86,7 +86,7 @@ void test_downstream_get_request_header(void) {
 }
 
 void test_downstream_get_response_header(void) {
-  Downstream d(nullptr, 0, 0);
+  Downstream d(nullptr, nullptr, 0, 0);
   d.add_response_header("alpha", "0");
   d.add_response_header(":status", "1");
   d.add_response_header("content-length", "2");
@@ -99,7 +99,7 @@ void test_downstream_get_response_header(void) {
 }
 
 void test_downstream_crumble_request_cookie(void) {
-  Downstream d(nullptr, 0, 0);
+  Downstream d(nullptr, nullptr, 0, 0);
   d.add_request_header(":method", "get");
   d.add_request_header(":path", "/");
   auto val = "alpha; bravo; ; ;; charlie;;";
@@ -122,7 +122,7 @@ void test_downstream_crumble_request_cookie(void) {
 }
 
 void test_downstream_assemble_request_cookie(void) {
-  Downstream d(nullptr, 0, 0);
+  Downstream d(nullptr, nullptr, 0, 0);
   d.add_request_header(":method", "get");
   d.add_request_header(":path", "/");
   d.add_request_header("cookie", "alpha");
@@ -135,7 +135,7 @@ void test_downstream_assemble_request_cookie(void) {
 
 void test_downstream_rewrite_location_response_header(void) {
   {
-    Downstream d(nullptr, 0, 0);
+    Downstream d(nullptr, nullptr, 0, 0);
     d.set_request_downstream_host("localhost:3000");
     d.add_request_header("host", "localhost");
     d.add_response_header("location", "http://localhost:3000/");
@@ -146,7 +146,7 @@ void test_downstream_rewrite_location_response_header(void) {
     CU_ASSERT("https://localhost/" == (*location).value);
   }
   {
-    Downstream d(nullptr, 0, 0);
+    Downstream d(nullptr, nullptr, 0, 0);
     d.set_request_downstream_host("localhost");
     d.set_request_http2_authority("localhost");
     d.add_response_header("location", "http://localhost:3000/");
diff --git a/src/shrpx_http2_upstream.cc b/src/shrpx_http2_upstream.cc
index f7915561..94dd3237 100644
--- a/src/shrpx_http2_upstream.cc
+++ b/src/shrpx_http2_upstream.cc
@@ -256,8 +256,11 @@ int on_begin_headers_callback(nghttp2_session *session,
                          << frame->hd.stream_id;
   }
 
+  auto handler = upstream->get_client_handler();
+
   // TODO Use priority 0 for now
-  auto downstream = make_unique<Downstream>(upstream, frame->hd.stream_id, 0);
+  auto downstream = make_unique<Downstream>(upstream, handler->get_mcpool(),
+                                            frame->hd.stream_id, 0);
   nghttp2_session_set_stream_user_data(session, frame->hd.stream_id,
                                        downstream.get());
 
@@ -484,6 +487,7 @@ int on_frame_send_callback(nghttp2_session *session, const nghttp2_frame *frame,
     verbose_on_frame_send_callback(session, frame, user_data);
   }
   auto upstream = static_cast<Http2Upstream *>(user_data);
+  auto handler = upstream->get_client_handler();
 
   switch (frame->hd.type) {
   case NGHTTP2_SETTINGS:
@@ -492,8 +496,9 @@ int on_frame_send_callback(nghttp2_session *session, const nghttp2_frame *frame,
     }
     return 0;
   case NGHTTP2_PUSH_PROMISE: {
-    auto downstream = make_unique<Downstream>(
-        upstream, frame->push_promise.promised_stream_id, 0);
+    auto downstream =
+        make_unique<Downstream>(upstream, handler->get_mcpool(),
+                                frame->push_promise.promised_stream_id, 0);
 
     downstream->disable_upstream_rtimer();
 
@@ -1498,8 +1503,6 @@ int Http2Upstream::on_downstream_reset(bool no_retry) {
   return 0;
 }
 
-MemchunkPool *Http2Upstream::get_mcpool() { return &mcpool_; }
-
 int Http2Upstream::prepare_push_promise(Downstream *downstream) {
   int rv;
   http_parser_url u;
diff --git a/src/shrpx_http2_upstream.h b/src/shrpx_http2_upstream.h
index 81b42563..ef8c0bee 100644
--- a/src/shrpx_http2_upstream.h
+++ b/src/shrpx_http2_upstream.h
@@ -79,8 +79,6 @@ public:
   virtual void on_handler_delete();
   virtual int on_downstream_reset(bool no_retry);
 
-  virtual MemchunkPool *get_mcpool();
-
   bool get_flow_control() const;
   // Perform HTTP/2 upgrade from |upstream|. On success, this object
   // takes ownership of the |upstream|. This function returns 0 if it
@@ -103,9 +101,7 @@ public:
   int on_request_headers(Downstream *downstream, const nghttp2_frame *frame);
 
 private:
-  // must be put before downstream_queue_
   std::unique_ptr<HttpsUpstream> pre_upstream_;
-  MemchunkPool mcpool_;
   DownstreamQueue downstream_queue_;
   ev_timer settings_timer_;
   ev_timer shutdown_timer_;
diff --git a/src/shrpx_https_upstream.cc b/src/shrpx_https_upstream.cc
index c760c5db..6a6ed2f2 100644
--- a/src/shrpx_https_upstream.cc
+++ b/src/shrpx_https_upstream.cc
@@ -64,8 +64,12 @@ int htp_msg_begin(http_parser *htp) {
     ULOG(INFO, upstream) << "HTTP request started";
   }
   upstream->reset_current_header_length();
+
+  auto handler = upstream->get_client_handler();
+
   // TODO specify 0 as priority for now
-  upstream->attach_downstream(make_unique<Downstream>(upstream, 0, 0));
+  upstream->attach_downstream(
+      make_unique<Downstream>(upstream, handler->get_mcpool(), 0, 0));
   return 0;
 }
 } // namespace
@@ -636,7 +640,8 @@ void HttpsUpstream::error_reply(unsigned int status_code) {
   auto downstream = get_downstream();
 
   if (!downstream) {
-    attach_downstream(make_unique<Downstream>(this, 1, 1));
+    attach_downstream(
+        make_unique<Downstream>(this, handler_->get_mcpool(), 1, 1));
     downstream = get_downstream();
   }
 
@@ -926,6 +931,4 @@ fail:
   return 0;
 }
 
-MemchunkPool *HttpsUpstream::get_mcpool() { return &mcpool_; }
-
 } // namespace shrpx
diff --git a/src/shrpx_https_upstream.h b/src/shrpx_https_upstream.h
index 820d462c..1b0c648a 100644
--- a/src/shrpx_https_upstream.h
+++ b/src/shrpx_https_upstream.h
@@ -76,8 +76,6 @@ public:
   virtual void on_handler_delete();
   virtual int on_downstream_reset(bool no_retry);
 
-  virtual MemchunkPool *get_mcpool();
-
   void reset_current_header_length();
   void log_response_headers(const std::string &hdrs) const;
 
@@ -85,8 +83,6 @@ private:
   ClientHandler *handler_;
   http_parser htp_;
   size_t current_header_length_;
-  // must be put before downstream_
-  MemchunkPool mcpool_;
   std::unique_ptr<Downstream> downstream_;
   IOControl ioctrl_;
 };
diff --git a/src/shrpx_spdy_upstream.cc b/src/shrpx_spdy_upstream.cc
index 4968a413..bf49c28f 100644
--- a/src/shrpx_spdy_upstream.cc
+++ b/src/shrpx_spdy_upstream.cc
@@ -797,7 +797,8 @@ int SpdyUpstream::error_reply(Downstream *downstream,
 
 Downstream *SpdyUpstream::add_pending_downstream(int32_t stream_id,
                                                  int32_t priority) {
-  auto downstream = make_unique<Downstream>(this, stream_id, priority);
+  auto downstream = make_unique<Downstream>(this, handler_->get_mcpool(),
+                                            stream_id, priority);
   spdylay_session_set_stream_user_data(session_, stream_id, downstream.get());
   auto res = downstream.get();
 
@@ -1080,6 +1081,4 @@ int SpdyUpstream::on_downstream_reset(bool no_retry) {
   return 0;
 }
 
-MemchunkPool *SpdyUpstream::get_mcpool() { return &mcpool_; }
-
 } // namespace shrpx
diff --git a/src/shrpx_spdy_upstream.h b/src/shrpx_spdy_upstream.h
index 2a6e37e1..2e4aec47 100644
--- a/src/shrpx_spdy_upstream.h
+++ b/src/shrpx_spdy_upstream.h
@@ -74,8 +74,6 @@ public:
   virtual void on_handler_delete();
   virtual int on_downstream_reset(bool no_retry);
 
-  virtual MemchunkPool *get_mcpool();
-
   bool get_flow_control() const;
 
   int consume(int32_t stream_id, size_t len);
@@ -84,8 +82,6 @@ public:
   void initiate_downstream(Downstream *downstream);
 
 private:
-  // must be put before downstream_queue_
-  MemchunkPool mcpool_;
   DownstreamQueue downstream_queue_;
   ClientHandler *handler_;
   spdylay_session *session_;
diff --git a/src/shrpx_upstream.h b/src/shrpx_upstream.h
index ad8e7420..fe9a673d 100644
--- a/src/shrpx_upstream.h
+++ b/src/shrpx_upstream.h
@@ -27,9 +27,6 @@
 
 #include "shrpx.h"
 #include "shrpx_io_control.h"
-#include "memchunk.h"
-
-using namespace nghttp2;
 
 namespace shrpx {
 
@@ -65,8 +62,6 @@ public:
   virtual void pause_read(IOCtrlReason reason) = 0;
   virtual int resume_read(IOCtrlReason reason, Downstream *downstream,
                           size_t consumed) = 0;
-
-  virtual MemchunkPool *get_mcpool() = 0;
 };
 
 } // namespace shrpx
diff --git a/src/shrpx_worker.cc b/src/shrpx_worker.cc
index f7d4d489..e84d456f 100644
--- a/src/shrpx_worker.cc
+++ b/src/shrpx_worker.cc
@@ -37,8 +37,6 @@
 #include "util.h"
 #include "template.h"
 
-using namespace nghttp2;
-
 namespace shrpx {
 
 namespace {
@@ -218,4 +216,6 @@ void Worker::set_graceful_shutdown(bool f) { graceful_shutdown_ = f; }
 
 bool Worker::get_graceful_shutdown() const { return graceful_shutdown_; }
 
+MemchunkPool *Worker::get_mcpool() { return &mcpool_; }
+
 } // namespace shrpx
diff --git a/src/shrpx_worker.h b/src/shrpx_worker.h
index 78ed18ac..43bb729b 100644
--- a/src/shrpx_worker.h
+++ b/src/shrpx_worker.h
@@ -42,6 +42,9 @@
 
 #include "shrpx_config.h"
 #include "shrpx_downstream_connection_pool.h"
+#include "memchunk.h"
+
+using namespace nghttp2;
 
 namespace shrpx {
 
@@ -104,6 +107,8 @@ public:
   void set_graceful_shutdown(bool f);
   bool get_graceful_shutdown() const;
 
+  MemchunkPool *get_mcpool();
+
 private:
   std::vector<std::unique_ptr<Http2Session>> http2sessions_;
   size_t next_http2session_;
@@ -113,6 +118,7 @@ private:
   std::mutex m_;
   std::deque<WorkerEvent> q_;
   ev_async w_;
+  MemchunkPool mcpool_;
   DownstreamConnectionPool dconn_pool_;
   WorkerStat worker_stat_;
   struct ev_loop *loop_;