diff --git a/heat/engine/resources/aws/cfn/stack.py b/heat/engine/resources/aws/cfn/stack.py
index 94b03d48f..cfc5ee401 100644
--- a/heat/engine/resources/aws/cfn/stack.py
+++ b/heat/engine/resources/aws/cfn/stack.py
@@ -61,7 +61,7 @@ class NestedStack(stack_resource.StackResource):
             raise ValueError(_("Could not fetch remote template '%(url)s': "
                              "%(exc)s") %
                              {'url': self.properties[self.TEMPLATE_URL],
-                              'exc': str(r_exc)})
+                              'exc': r_exc})
 
         return template_format.parse(template_data)
 
@@ -105,7 +105,7 @@ class NestedStack(stack_resource.StackResource):
             raise ValueError(_("Could not fetch remote template '%(url)s': "
                              "%(exc)s") %
                              {'url': self.properties[self.TEMPLATE_URL],
-                              'exc': str(r_exc)})
+                              'exc': r_exc})
 
         template = template_format.parse(template_data)
 
diff --git a/heat/engine/volume_tasks.py b/heat/engine/volume_tasks.py
index e19f9bd52..0a0c4f494 100644
--- a/heat/engine/volume_tasks.py
+++ b/heat/engine/volume_tasks.py
@@ -49,7 +49,7 @@ class VolumeExtendTask(object):
             if self.clients.client_plugin('cinder').is_client_exception(ex):
                 raise exception.Error(_(
                     "Failed to extend volume %(vol)s - %(err)s") % {
-                        'vol': vol.id, 'err': str(ex)})
+                        'vol': vol.id, 'err': ex})
             else:
                 raise