diff --git a/Lib/asyncore.py b/Lib/asyncore.py
index 88845012e48..44e89181cb6 100644
--- a/Lib/asyncore.py
+++ b/Lib/asyncore.py
@@ -61,8 +61,8 @@ except NameError:
 
 def _strerror(err):
     try:
-        return strerror(err)
-    except (ValueError, OverflowError):
+        return os.strerror(err)
+    except (ValueError, OverflowError, NameError):
         if err in errorcode:
             return errorcode[err]
         return "Unknown error %s" %err
diff --git a/Lib/test/test_asyncore.py b/Lib/test/test_asyncore.py
index 4db29ca14ea..785b2116f6f 100644
--- a/Lib/test/test_asyncore.py
+++ b/Lib/test/test_asyncore.py
@@ -6,6 +6,7 @@ import socket
 import threading
 import sys
 import time
+import errno
 
 from test import support
 from test.support import TESTFN, run_unittest, unlink
@@ -315,6 +316,14 @@ class DispatcherTests(unittest.TestCase):
         # test cheap inheritance with the underlying socket
         self.assertEqual(d.family, socket.AF_INET)
 
+    def test_strerror(self):
+        # refers to bug #8573
+        err = asyncore._strerror(errno.EPERM)
+        if hasattr(os, 'strerror'):
+            self.assertEqual(err, os.strerror(errno.EPERM))
+        err = asyncore._strerror(-1)
+        self.assertTrue("unknown error" in err.lower())
+
 
 class dispatcherwithsend_noread(asyncore.dispatcher_with_send):
     def readable(self):