diff --git a/mio/bin/t03.c b/mio/bin/t03.c
index 3ebe603..1cb2215 100644
--- a/mio/bin/t03.c
+++ b/mio/bin/t03.c
@@ -90,7 +90,7 @@ static int on_json_inst (mio_json_t* json, mio_json_inst_t inst,	mio_oow_t level
 	return 0;
 }
 
-static int write_json_element (mio_jsonwr_t* jsonwr, const mio_bch_t* dptr, mio_oow_t dlen)
+static int write_json_element (mio_jsonwr_t* jsonwr, const mio_bch_t* dptr, mio_oow_t dlen, void* ctx)
 {
 	write (1, dptr, dlen);
 	return 0;
@@ -146,7 +146,7 @@ int main (int argc, char* argv[])
 	
 		jsonwr = mio_jsonwr_open (mio, 0);
 
-		mio_jsonwr_setwritecb (jsonwr, write_json_element);
+		mio_jsonwr_setwritecb (jsonwr, write_json_element, MIO_NULL);
 
 		mio_jsonwr_startarray (jsonwr);
 		
diff --git a/mio/lib/json.c b/mio/lib/json.c
index aee8a9d..6ff2695 100644
--- a/mio/lib/json.c
+++ b/mio/lib/json.c
@@ -815,7 +815,7 @@ void mio_jsonwr_close (mio_jsonwr_t* jsonwr)
 	mio_freemem (jsonwr->mio, jsonwr);
 }
 
-static int write_nothing (mio_jsonwr_t* jsonwr, const mio_bch_t* dptr, mio_oow_t dlen)
+static int write_nothing (mio_jsonwr_t* jsonwr, const mio_bch_t* dptr, mio_oow_t dlen, void* ctx)
 {
 	return 0;
 }
@@ -837,7 +837,7 @@ static int flush_wbuf (mio_jsonwr_t* jsonwr)
 {
 	int ret = 0;
 
-	if (jsonwr->writecb(jsonwr, jsonwr->wbuf, jsonwr->wbuf_len) <= -1) ret = -1;
+	if (jsonwr->writecb(jsonwr, jsonwr->wbuf, jsonwr->wbuf_len, jsonwr->wctx) <= -1) ret = -1;
 	jsonwr->wbuf_len = 0; /* reset the buffer length regardless of writing result */
 
 	return ret;
@@ -851,9 +851,10 @@ void mio_jsonwr_fini (mio_jsonwr_t* jsonwr)
 
 /* ========================================================================= */
 
-void mio_jsonwr_setwritecb (mio_jsonwr_t* jsonwr, mio_jsonwr_writecb_t writecb)
+void mio_jsonwr_setwritecb (mio_jsonwr_t* jsonwr, mio_jsonwr_writecb_t writecb, void* ctx)
 {
 	jsonwr->writecb = writecb;
+	jsonwr->wctx = ctx;
 }
 
 static int escape_char (mio_uch_t uch, mio_uch_t* xch)
diff --git a/mio/lib/mio-json.h b/mio/lib/mio-json.h
index e5f3e9a..c58bec0 100644
--- a/mio/lib/mio-json.h
+++ b/mio/lib/mio-json.h
@@ -133,9 +133,9 @@ typedef struct mio_jsonwr_t mio_jsonwr_t;
 
 typedef int (*mio_jsonwr_writecb_t) (
 	mio_jsonwr_t*         jsonwr,
-	/*mio_oow_t           level,*/
 	const mio_bch_t*      dptr,
-	mio_oow_t             dlen
+	mio_oow_t             dlen,
+	void*                 ctx
 );
 
 typedef struct mio_jsonwr_state_node_t mio_jsonwr_state_node_t;
@@ -156,6 +156,7 @@ struct mio_jsonwr_t
 	mio_jsonwr_state_node_t* state_stack;
 	int pretty;
 
+	void* wctx;	
 	mio_bch_t wbuf[8192];
 	mio_oow_t wbuf_len;
 };
@@ -265,7 +266,8 @@ static MIO_INLINE void* mio_jsonwr_getxtn (mio_jsonwr_t* jsonwr) { return (void*
 
 MIO_EXPORT void mio_jsonwr_setwritecb (
 	mio_jsonwr_t*        jsonwr,
-	mio_jsonwr_writecb_t writecb
+	mio_jsonwr_writecb_t writecb,
+	void*                ctx
 );
 
 MIO_EXPORT int mio_jsonwr_write (