diff --git a/lib/pure/ioselects/ioselectors_select.nim b/lib/pure/ioselects/ioselectors_select.nim
index 2f22f1b305..eed64a34db 100644
--- a/lib/pure/ioselects/ioselectors_select.nim
+++ b/lib/pure/ioselects/ioselectors_select.nim
@@ -110,6 +110,7 @@ proc close*[T](s: Selector[T]) =
   when hasThreadSupport:
     deallocSharedArray(s.fds)
     deallocShared(cast[pointer](s))
+    deinitLock(s.lock)
 
 when defined(windows):
   proc newSelectEvent*(): SelectEvent =
diff --git a/lib/system/threads.nim b/lib/system/threads.nim
index 6b858c4bba..bf93b5e01d 100644
--- a/lib/system/threads.nim
+++ b/lib/system/threads.nim
@@ -41,6 +41,8 @@
 ##  for i in 0..high(thr):
 ##    createThread(thr[i], threadFunc, (i*10, i*10+5))
 ##  joinThreads(thr)
+## 
+##  deinitLock(L)
 
 when not declared(ThisIsSystem):
   {.error: "You must not import this module explicitly".}