diff --git a/lib/system.nim b/lib/system.nim
index d37a8460e3..784e072a89 100644
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -687,6 +687,8 @@ proc len*[T](x: seq[T]): int {.magic: "LengthSeq", noSideEffect.}
   ## .. code-block:: nim
   ##  var arr = [1,1,1,1,1]
   ##  len(arr) #=> 5
+  ##  for i in 0..<arr.len:
+  ##    echo arr[i] #=> 1,1,1,1,1
 
 # set routines:
 proc incl*[T](x: var set[T], y: T) {.magic: "Incl", noSideEffect.}