diff --git a/asyncdispatch2/transports/datagram.nim b/asyncdispatch2/transports/datagram.nim
index 008e8023..1fdc64c9 100644
--- a/asyncdispatch2/transports/datagram.nim
+++ b/asyncdispatch2/transports/datagram.nim
@@ -535,7 +535,7 @@ proc send*(transp: DatagramTransport, pbytes: pointer,
     transp.resumeWrite()
   return retFuture
 
-proc send*(transp: DatagramTransport, msg: string): Future[void] =
+proc send*(transp: DatagramTransport, msg: var string): Future[void] =
   ## Send string ``msg`` using transport ``transp`` to remote destination
   ## address which was bounded on transport.
   var retFuture = FutureGCString[void]()
@@ -549,7 +549,7 @@ proc send*(transp: DatagramTransport, msg: string): Future[void] =
     transp.resumeWrite()
   return retFuture
 
-proc send*[T](transp: DatagramTransport, msg: seq[T]): Future[void] =
+proc send*[T](transp: DatagramTransport, msg: var seq[T]): Future[void] =
   ## Send string ``msg`` using transport ``transp`` to remote destination
   ## address which was bounded on transport.
   var retFuture = FutureGCSeq[void, T]()
@@ -576,7 +576,7 @@ proc sendTo*(transp: DatagramTransport, pbytes: pointer, nbytes: int,
     transp.resumeWrite()
   return retFuture
 
-proc sendTo*(transp: DatagramTransport, msg: string,
+proc sendTo*(transp: DatagramTransport, msg: var string,
              remote: TransportAddress): Future[void] =
   ## Send string ``msg`` using transport ``transp`` to remote destination
   ## address ``remote``.
@@ -592,7 +592,7 @@ proc sendTo*(transp: DatagramTransport, msg: string,
     transp.resumeWrite()
   return retFuture
 
-proc sendTo*[T](transp: DatagramTransport, msg: seq[T],
+proc sendTo*[T](transp: DatagramTransport, msg: var seq[T],
                 remote: TransportAddress): Future[void] =
   ## Send sequence ``msg`` using transport ``transp`` to remote destination
   ## address ``remote``.
diff --git a/asyncdispatch2/transports/stream.nim b/asyncdispatch2/transports/stream.nim
index 0d227647..e875c8c7 100644
--- a/asyncdispatch2/transports/stream.nim
+++ b/asyncdispatch2/transports/stream.nim
@@ -882,7 +882,7 @@ proc write*(transp: StreamTransport, pbytes: pointer,
     transp.resumeWrite()
   return retFuture
 
-proc write*(transp: StreamTransport, msg: string): Future[int] =
+proc write*(transp: StreamTransport, msg: var string): Future[int] =
   ## Write data from string ``msg`` using transport ``transp``.
   var retFuture = FutureGCString[int]()
   transp.checkClosed(retFuture)
@@ -895,7 +895,7 @@ proc write*(transp: StreamTransport, msg: string): Future[int] =
     transp.resumeWrite()
   return retFuture
 
-proc write*[T](transp: StreamTransport, msg: seq[T]): Future[int] =
+proc write*[T](transp: StreamTransport, msg: var seq[T]): Future[int] =
   ## Write sequence ``msg`` using transport ``transp``.
   var retFuture = FutureGCSeq[int, T]()
   transp.checkClosed(retFuture)
diff --git a/tests/testserver.nim b/tests/testserver.nim
index 813b6313..8343d84f 100644
--- a/tests/testserver.nim
+++ b/tests/testserver.nim
@@ -40,7 +40,8 @@ proc serveUdataStreamClient(server: StreamServer,
                             transp: StreamTransport) {.async.} =
   var udata = getUserData[CustomData](server)
   var line = await transp.readLine()
-  discard await transp.write(line & udata.test & "\r\n")
+  var msg = line & udata.test & "\r\n"
+  discard await transp.write(msg)
   transp.close()
 
 proc customServerTransport(server: StreamServer,