diff --git a/ceilometer/tests/tempest/exceptions.py b/ceilometer/tests/tempest/exceptions.py
index 92f335f995..de22a417dd 100644
--- a/ceilometer/tests/tempest/exceptions.py
+++ b/ceilometer/tests/tempest/exceptions.py
@@ -119,7 +119,7 @@ class ServerUnreachable(TempestException):
 # of get_network_from_name and preprov_creds to tempest.lib, and it should
 # be migrated along with them
 class InvalidTestResource(TempestException):
-    message = "%(name) is not a valid %(type), or the name is ambiguous"
+    message = "%(name)s is not a valid %(type)s, or the name is ambiguous"
 
 
 class RFCViolation(RestClientException):