diff --git a/keystone/openstack/common/db/exception.py b/keystone/openstack/common/db/exception.py
index b57657fb88..0aa7df0536 100644
--- a/keystone/openstack/common/db/exception.py
+++ b/keystone/openstack/common/db/exception.py
@@ -16,6 +16,8 @@
 
 """DB related custom exceptions."""
 
+import six
+
 from keystone.openstack.common.gettextutils import _
 
 
@@ -23,7 +25,7 @@ class DBError(Exception):
     """Wraps an implementation specific exception."""
     def __init__(self, inner_exception=None):
         self.inner_exception = inner_exception
-        super(DBError, self).__init__(str(inner_exception))
+        super(DBError, self).__init__(six.text_type(inner_exception))
 
 
 class DBDuplicateEntry(DBError):
@@ -46,7 +48,7 @@ class DBInvalidUnicodeParameter(Exception):
 class DbMigrationError(DBError):
     """Wraps migration specific exception."""
     def __init__(self, message=None):
-        super(DbMigrationError, self).__init__(str(message))
+        super(DbMigrationError, self).__init__(message)
 
 
 class DBConnectionError(DBError):