diff --git a/src/python/dm/common/client/sessionManager.py b/src/python/dm/common/client/sessionManager.py
index e5c14d9fa6569c935002974bd1eb529075611d34..e99b05b33c7a32d504433d966241cae0d9d765af 100755
--- a/src/python/dm/common/client/sessionManager.py
+++ b/src/python/dm/common/client/sessionManager.py
@@ -68,7 +68,7 @@ class SessionManager:
         self.logger.debug('User %s session cookie: %s' % (username, self.sessionCookie))
 
     def getUsername(self, username):
-        if not len(username) and self.requireSessionCredentials:
+        if username is None and self.requireSessionCredentials:
             return self.askForUsername()
         return username
 
@@ -81,7 +81,7 @@ class SessionManager:
         return username
 
     def getPassword(self, password):
-        if not len(password) and self.requireSessionCredentials:
+        if password is None and self.requireSessionCredentials:
             return self.askForPassword()
         return password