diff --git a/lib/pure/sockets.nim b/lib/pure/sockets.nim
index 684def9786..66bb1e6a9e 100644
--- a/lib/pure/sockets.nim
+++ b/lib/pure/sockets.nim
@@ -131,7 +131,7 @@ type
 
   ETimeout* = object of ESynch
 
-const
+let
   InvalidSocket*: TSocket = nil ## invalid socket
 
 when defined(windows):