diff --git a/_glua-tests/issues.lua b/_glua-tests/issues.lua
index 0bb77bcd..65a2c7f4 100644
--- a/_glua-tests/issues.lua
+++ b/_glua-tests/issues.lua
@@ -468,4 +468,15 @@ function test()
   end)
   assert(not ok)
 end
-test()
\ No newline at end of file
+test()
+
+-- issue #459
+function test()
+  local a, b = io.popen("ls", nil)
+  assert(a)
+  assert(b == nil)
+  local a, b = io.popen("ls", nil, nil)
+  assert(a)
+  assert(b == nil)
+end
+test()
diff --git a/iolib.go b/iolib.go
index b59e82b2..3f5f295c 100644
--- a/iolib.go
+++ b/iolib.go
@@ -658,6 +658,9 @@ func ioPopen(L *LState) int {
 	cmd := L.CheckString(1)
 	if L.GetTop() == 1 {
 		L.Push(LString("r"))
+	} else if L.GetTop() > 1 && (L.Get(2)).Type() == LTNil {
+		L.SetTop(1)
+		L.Push(LString("r"))
 	}
 	var file *LUserData
 	var err error