diff --git a/examples/app/asyncutils.nim b/examples/app/asyncutils.nim
index 30a716e..6b510d7 100644
--- a/examples/app/asyncutils.nim
+++ b/examples/app/asyncutils.nim
@@ -74,7 +74,7 @@ proc asyncRecvMsg*(fd: AsyncFD, size: int = BufferSize,
       var cmsg = ControlMessage(level: cmsgHeader.cmsg_level,
                                 msgType: cmsgHeader.cmsg_type,
                                 data: newString(dataLen))
-      copyMem(cmsg.data.cstring, CMSG_DATA(cmsgHeader), cmsgHeader.cmsg_len)
+      copyMem(cmsg.data.cstring, CMSG_DATA(cmsgHeader), dataLen)
       cmsgs.add(cmsg)
       cmsgHeader = CMSG_NXTHDR(addr msg, cmsgHeader)