diff --git a/csources b/csources
new file mode 160000
index 0000000000..b0bcf88e26
--- /dev/null
+++ b/csources
@@ -0,0 +1 @@
+Subproject commit b0bcf88e26730b23d22e2663adf1babb05bd5a71
diff --git a/lib/posix/posix.nim b/lib/posix/posix.nim
index c3085f0fbc..8c1c258dbb 100644
--- a/lib/posix/posix.nim
+++ b/lib/posix/posix.nim
@@ -2382,7 +2382,7 @@ proc hstrerror*(herrnum: cint): cstring {.importc, header: "<netdb.h>".}
 proc FD_CLR*(a1: cint, a2: var TFdSet) {.importc, header: "<sys/select.h>".}
 proc FD_ISSET*(a1: cint | SocketHandle, a2: var TFdSet): cint {.
   importc, header: "<sys/select.h>".}
-proc fdSet*(a1: cint | SocketHandle, a2: var TFdSet) {.
+proc FD_SET*(a1: cint | SocketHandle, a2: var TFdSet) {.
   importc: "FD_SET", header: "<sys/select.h>".}
 proc FD_ZERO*(a1: var TFdSet) {.importc, header: "<sys/select.h>".}
 
diff --git a/lib/pure/asyncio.nim b/lib/pure/asyncio.nim
index bb0d29fc4b..0dbc0a3d5f 100644
--- a/lib/pure/asyncio.nim
+++ b/lib/pure/asyncio.nim
@@ -91,11 +91,11 @@ import sockets, os
 ##      getSocket(s).accept(client)
 
 when defined(windows):
-  from winlean import TimeVal, SocketHandle, fdSet, FD_ZERO, TFdSet,
-    fdSet, FD_ISSET, select
+  from winlean import TimeVal, SocketHandle, FD_SET, FD_ZERO, TFdSet,
+    FD_ISSET, select
 else:
-  from posix import TimeVal, SocketHandle, fdSet, FD_ZERO, TFdSet,
-    fdSet, FD_ISSET, select
+  from posix import TimeVal, SocketHandle, FD_SET, FD_ZERO, TFdSet,
+    FD_ISSET, select
 
 type
   DelegateObj* = object
@@ -556,7 +556,7 @@ proc createFdSet(fd: var TFdSet, s: seq[Delegate], m: var int) =
   FD_ZERO(fd)
   for i in items(s): 
     m = max(m, int(i.fd))
-    fdSet(i.fd, fd)
+    FD_SET(i.fd, fd)
    
 proc pruneSocketSet(s: var seq[Delegate], fd: var TFdSet) =
   var i = 0
diff --git a/lib/pure/rawsockets.nim b/lib/pure/rawsockets.nim
index 5756ca23d5..62a011999b 100644
--- a/lib/pure/rawsockets.nim
+++ b/lib/pure/rawsockets.nim
@@ -372,7 +372,7 @@ proc createFdSet(fd: var TFdSet, s: seq[SocketHandle], m: var int) =
   FD_ZERO(fd)
   for i in items(s): 
     m = max(m, int(i))
-    fdSet(i, fd)
+    FD_SET(i, fd)
    
 proc pruneSocketSet(s: var seq[SocketHandle], fd: var TFdSet) = 
   var i = 0
diff --git a/lib/pure/sockets.nim b/lib/pure/sockets.nim
index 6975f07c0f..36389edcc0 100644
--- a/lib/pure/sockets.nim
+++ b/lib/pure/sockets.nim
@@ -936,7 +936,7 @@ proc createFdSet(fd: var TFdSet, s: seq[Socket], m: var int) =
   FD_ZERO(fd)
   for i in items(s): 
     m = max(m, int(i.fd))
-    fdSet(i.fd, fd)
+    FD_SET(i.fd, fd)
    
 proc pruneSocketSet(s: var seq[Socket], fd: var TFdSet) =
   var i = 0
diff --git a/lib/windows/winlean.nim b/lib/windows/winlean.nim
index cc633d90ba..76d17bc4a2 100644
--- a/lib/windows/winlean.nim
+++ b/lib/windows/winlean.nim
@@ -536,7 +536,7 @@ proc WSAFDIsSet(s: SocketHandle, set: var TFdSet): bool {.
 proc FD_ISSET*(socket: SocketHandle, set: var TFdSet): cint = 
   result = if WSAFDIsSet(socket, set): 1'i32 else: 0'i32
 
-proc fdSet*(socket: SocketHandle, s: var TFdSet) = 
+proc FD_SET*(socket: SocketHandle, s: var TFdSet) = 
   if s.fd_count < FD_SETSIZE:
     s.fd_array[int(s.fd_count)] = socket
     inc(s.fd_count)