diff --git a/ccserver/jobs.py b/ccserver/jobs.py
index ccf96a841528dd010be949d98500415c64148799..c525bfbd059ecba1993088dd4b5290c5eb97f418 100644
--- a/ccserver/jobs.py
+++ b/ccserver/jobs.py
@@ -306,7 +306,7 @@ class JobsManager(object):
         job = self._jobs.get(jobid)
 
         if job is None:
-            raise UnknownJobError('Jobid %r is unknown' % jobid)
+            raise UnknownJobError('Invalid job id: %r' % jobid)
         else:
             job.cancel()