diff --git a/nova/api/openstack/compute/contrib/coverage_ext.py b/nova/api/openstack/compute/contrib/coverage_ext.py
index d77dff6c8e..a69ef93673 100644
--- a/nova/api/openstack/compute/contrib/coverage_ext.py
+++ b/nova/api/openstack/compute/contrib/coverage_ext.py
@@ -215,7 +215,7 @@ class CoverageController(object):
                 coverInst.xml_report(outfile=path)
             elif html:
                 if os.path.isdir(path):
-                    msg = _("Directory conflict: %s already exists")
+                    msg = _("Directory conflict: %s already exists") % path
                     raise exc.HTTPBadRequest(explanation=msg)
                 coverInst.html_report(directory=path)
             else:
diff --git a/nova/api/openstack/compute/plugins/v3/coverage.py b/nova/api/openstack/compute/plugins/v3/coverage.py
index 90c02b6f27..43763ffab9 100644
--- a/nova/api/openstack/compute/plugins/v3/coverage.py
+++ b/nova/api/openstack/compute/plugins/v3/coverage.py
@@ -248,7 +248,7 @@ class CoverageController(wsgi.Controller):
                 coverInst.xml_report(outfile=path)
             elif html:
                 if os.path.isdir(path):
-                    msg = _("Directory conflict: %s already exists")
+                    msg = _("Directory conflict: %s already exists") % path
                     raise exc.HTTPBadRequest(explanation=msg)
                 coverInst.html_report(directory=path)
             else: