diff --git a/src/falcon/rr_hctg_track.nim b/src/falcon/rr_hctg_track.nim
index e0ec6d6..340620b 100644
--- a/src/falcon/rr_hctg_track.nim
+++ b/src/falcon/rr_hctg_track.nim
@@ -60,16 +60,16 @@ proc tostring(src: str9, dst: var string) =
 proc hash(x: str9): hashes.Hash =
   return hashes.hash(tostring(x))
 
-proc unpack_type*(ss: streams.Stream, x: var str9) =
+proc unpack_type*(ss: var msgpack4nim.MsgStream, x: var str9) =
   var str: string
   msgpack4nim.unpack(ss, str)
   copyMem(addr x[0], addr str[0], 9)
 
-proc pack_type*(ss: streams.Stream, x: str9) =
+proc pack_type*(ss: var msgpack4nim.MsgStream, x: str9) =
   let str: string = tostring(x)
   msgpack4nim.pack(ss, str)
 
-proc pack_type*(ss: streams.Stream, x: binaryheap.Heap[mytuple]) =
+proc pack_type*(ss: var msgpack4nim.MsgStream, x: binaryheap.Heap[mytuple]) =
   let xseq: seq[mytuple] = sequtils.toSeq(binaryheap.items(x)) # unsorted
   msgpack4nim.pack(ss, xseq)
 proc `$`(x: str9): string =
@@ -409,10 +409,11 @@ proc run_tr_stage1(db_fn, fn: string, min_len, bestn: int): string =
   osproc.close(la4falcon_proc)
   let fn_rtn = "$#.rr_hctg_track.partial.msgpack" % [fn]
   log("Serialize '$#'" % [fn_rtn])
+  var msgss = msgpack4nim.initMsgStream() #you can pass some buffer capacity here https://github.com/jangko/msgpack4nim/issues/18
+  msgpack4nim.pack(msgss, rtn)
   var ss = streams.newFileStream(fn_rtn, system.fmWrite)
   defer: ss.close()
-  #ss.write($rtn)
-  msgpack4nim.pack(ss, rtn)
+  ss.write(msgss.data)
   return fn_rtn
 
 proc spawned_tr_stage1(db_fn, fn: string, min_len, bestn: int): string {.thread} =