diff --git a/src/socket.ts b/src/socket.ts
index 6c757ad..a408ea8 100644
--- a/src/socket.ts
+++ b/src/socket.ts
@@ -36,7 +36,8 @@ export function validateCertificate(
   dnsName: string
 ) {
   return (hostname: string, cert: tls.PeerCertificate): Error | undefined => {
-    if (serverCaMode === 'GOOGLE_MANAGED_CAS_CA') {
+    if (serverCaMode === 'GOOGLE_MANAGED_CAS_CA'
+      || serverCaMode === 'CUSTOMER_MANAGED_CAS_CA') {
       return tls.checkServerIdentity(dnsName, cert);
     }
     if (!cert || !cert.subject) {