diff --git a/agent/agent.go b/agent/agent.go
index 8d21db7c2..35403a145 100644
--- a/agent/agent.go
+++ b/agent/agent.go
@@ -525,7 +525,13 @@ func (a *Agent) listenAndServeGRPC() error {
 	a.xdsServer.Initialize()
 
 	var err error
-	a.grpcServer, err = a.xdsServer.GRPCServer(a.config.CertFile, a.config.KeyFile)
+	if a.config.HTTPSPort > 0 {
+		// gRPC uses the same TLS settings as the HTTPS API. If HTTPS is
+		// enabled then gRPC will require HTTPS as well.
+		a.grpcServer, err = a.xdsServer.GRPCServer(a.config.CertFile, a.config.KeyFile)
+	} else {
+		a.grpcServer, err = a.xdsServer.GRPCServer("", "")
+	}
 	if err != nil {
 		return err
 	}