diff --git a/CHANGES b/CHANGES
index 51dc96d..2be9953 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4,9 +4,12 @@ Released 2.4.28 2016-11-17
 Changes since 2.4.27:
 
 Lib/
+* LDAPObject.unbind_ext_s() invokes LDAPObject._trace_file.flush()
+  only if LDAPObject._trace_level is non-zero and Python is running
+  in debug mode
 * LDAPObject.unbind_ext_s() now ignores AttributeError
-  in case _trace_file has no flush() method
-* added dummy method logging_file_class.flush() because
+  in case LDAPObject._trace_file has no flush() method
+* added dummy method ldap.logger.logging_file_class.flush() because
   LDAPObject.unbind_ext_s() invokes it
 
 ----------------------------------------------------------------
@@ -1293,4 +1296,4 @@ Released 2.0.0pre02 2002-02-01
 ----------------------------------------------------------------
 Released 1.10alpha3 2000-09-19
 
-$Id: CHANGES,v 1.397 2016/11/17 12:08:59 stroeder Exp $
+$Id: CHANGES,v 1.398 2016/11/18 07:01:45 stroeder Exp $
diff --git a/Lib/ldap/ldapobject.py b/Lib/ldap/ldapobject.py
index 9b87787..188405c 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 1.157 2016/11/17 12:08:30 stroeder Exp $
+\$Id: ldapobject.py,v 1.158 2016/11/18 07:01:45 stroeder Exp $
 
 Compability:
 - Tested with Python 2.0+ but should work with Python 1.5.x
@@ -636,10 +636,11 @@ def unbind_ext_s(self,serverctrls=None,clientctrls=None):
       result = self.result3(msgid,all=1,timeout=self.timeout)
     else:
       result = None
-    try:
-      self._trace_file.flush()
-    except AttributeError:
-      pass
+    if __debug__ and self._trace_level>=1:
+      try:
+        self._trace_file.flush()
+      except AttributeError:
+        pass
     return result
 
   def unbind(self):