diff --git a/CHANGES b/CHANGES
index a758fad..7300d01 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4,6 +4,8 @@ Released 2.4.28 2016-11-xx
 Changes since 2.4.27:
 
 Lib/
+* LDAPObject.unbind_ext_s() now ignores AttributeError
+  in case _trace_file has no flush() method
 * added dummy method logging_file_class.flush() because
   LDAPObject.unbind_ext_s() invokes it
 
@@ -1291,4 +1293,4 @@ Released 2.0.0pre02 2002-02-01
 ----------------------------------------------------------------
 Released 1.10alpha3 2000-09-19
 
-$Id: CHANGES,v 1.395 2016/11/11 14:42:18 stroeder Exp $
+$Id: CHANGES,v 1.396 2016/11/17 12:08:30 stroeder Exp $
diff --git a/Lib/ldap/ldapobject.py b/Lib/ldap/ldapobject.py
index 13ea9e5..9b87787 100644
--- a/Lib/ldap/ldapobject.py
+++ b/Lib/ldap/ldapobject.py
@@ -3,7 +3,7 @@
 
 See http://www.python-ldap.org/ for details.
 
-\$Id: ldapobject.py,v 1.156 2016/07/24 16:22:32 stroeder Exp $
+\$Id: ldapobject.py,v 1.157 2016/11/17 12:08:30 stroeder Exp $
 
 Compability:
 - Tested with Python 2.0+ but should work with Python 1.5.x
@@ -636,7 +636,10 @@ def unbind_ext_s(self,serverctrls=None,clientctrls=None):
       result = self.result3(msgid,all=1,timeout=self.timeout)
     else:
       result = None
-    self._trace_file.flush()
+    try:
+      self._trace_file.flush()
+    except AttributeError:
+      pass
     return result
 
   def unbind(self):