diff --git a/src/shrpx_client_handler.h b/src/shrpx_client_handler.h
index 0eb66e54..138899df 100644
--- a/src/shrpx_client_handler.h
+++ b/src/shrpx_client_handler.h
@@ -135,7 +135,7 @@ public:
                        int64_t body_bytes_sent);
   WorkerStat *get_worker_stat() const;
 
-  using WriteBuf = RingBuf<16384>;
+  using WriteBuf = RingBuf<65536>;
   using ReadBuf = RingBuf<8192>;
 
   WriteBuf *get_wb();
diff --git a/src/shrpx_http2_session.h b/src/shrpx_http2_session.h
index a5df3b81..422f876d 100644
--- a/src/shrpx_http2_session.h
+++ b/src/shrpx_http2_session.h
@@ -168,8 +168,8 @@ public:
     CONNECTION_CHECK_STARTED
   };
 
-  using WriteBuf = RingBuf<16384>;
   using ReadBuf = RingBuf<8192>;
+  using WriteBuf = RingBuf<65536>;
 
 private:
   ev_io wev_;