diff --git a/api-ref/src/wadls/compute-api/src/v2.1/common.ent b/api-ref/src/wadls/compute-api/src/v2.1/common.ent
index 106b3ea5e..5ee6667cd 100644
--- a/api-ref/src/wadls/compute-api/src/v2.1/common.ent
+++ b/api-ref/src/wadls/compute-api/src/v2.1/common.ent
@@ -158,7 +158,7 @@
    xml:lang="EN"
    xmlns:wadl="http://wadl.dev.java.net/2009/02">
     <para>
-      The certificate ID, as a string. A valid value is <code>root</code>.
+      The certificate ID, as a string. The only valid value is <code>root</code>.
    </para>
   </wadl:doc>
 </param>'>