fixes #1646

tests/parallel/t5000.nim

@@ -0,0 +1,22 @@
+discard """
+  output: '''50005000'''
+"""
+
+import threadpool, strutils
+
+proc foo(x: int): string = $x
+
+proc main() =
+  var a = newSeq[int]()
+  for i in 1..10000:
+    add(a, i)
+
+  var s = 0
+  for i in a:
+    s += parseInt(^spawn(foo(i)))
+  echo s
+
+setMaxPoolSize 2
+
+parallel:
+  spawn main()