diff --git a/membership.lua b/membership.lua
index 14fa0de..9b31d9b 100755
--- a/membership.lua
+++ b/membership.lua
@@ -748,7 +748,7 @@ local function mark_left(uri_to_leave)
 
     -- Perform artificial events.generate() and instantly send it
     local myself = members.get(uri_to_leave)
-    if not myself then
+    if not myself or myself.status == opts.LEFT then
         return false
     end
     local event = events.pack({
diff --git a/test/test_quit.py b/test/test_quit.py
index 2b5af12..54a7161 100644
--- a/test/test_quit.py
+++ b/test/test_quit.py
@@ -25,3 +25,9 @@ def test_mark_left(servers, helpers):
     helpers.wait_for(servers[13301].check_status, ['localhost:13302', 'alive'])
     assert servers[13301].conn.eval('return membership.mark_left("localhost:13302")')[0]
     helpers.wait_for(servers[13301].check_status, ['localhost:13302', 'left'])
+
+    # already has left
+    assert not servers[13301].conn.eval('return membership.mark_left("localhost:13302")')[0]
+
+    # there are no such member
+    assert not servers[13301].conn.eval('return membership.mark_left("localhost:10000")')[0]