diff --git a/pkg/cloudcommon/policy/policy.go b/pkg/cloudcommon/policy/policy.go
index 7517dfa087..56418e3550 100644
--- a/pkg/cloudcommon/policy/policy.go
+++ b/pkg/cloudcommon/policy/policy.go
@@ -233,7 +233,8 @@ func (manager *SPolicyManager) explainPolicy(userCred mcclient.TokenCredential,
 	}
 	if len(policySeq) > 4 {
 		for i := 4; i < len(policySeq); i += 1 {
-			extra[i-4], _ = policySeq[i].GetString()
+			ev, _ := policySeq[i].GetString()
+			extra = append(extra, ev)
 		}
 	}