--- a/include/h2o/http2_internal.h
+++ b/include/h2o/http2_internal.h
@@ -33,7 +33,7 @@
 typedef struct st_h2o_http2_conn_t h2o_http2_conn_t;
 typedef struct st_h2o_http2_stream_t h2o_http2_stream_t;
 
-#define H2O_HTTP2_DEFAULT_OUTBUF_SIZE 81920 /* the target size of each write call; connection flow control window + alpha */
+#define H2O_HTTP2_DEFAULT_OUTBUF_SIZE 8192 /* the target size of each write call; connection flow control window + alpha */
 #define H2O_HTTP2_DEFAULT_OUTBUF_SOFT_MAX_SIZE 524288 /* 512KB; stops reading if size exceeds this value */
 
 /* hpack */