--- a/testing/marionette/driver.js
+++ b/testing/marionette/driver.js
@@ -738,17 +738,17 @@ GeckoDriver.prototype.listeningPromise =
  *
  * @throws {SessionNotCreatedError}
  *     If, for whatever reason, a session could not be created.
  */
 GeckoDriver.prototype.newSession = async function(cmd) {
   if (this.sessionID) {
     throw new SessionNotCreatedError("Maximum number of active sessions");
   }
-  this.sessionID = element.generateUUID();
+  this.sessionID = WebElement.generateUUID();
   this.newSessionCommandId = cmd.id;
 
   try {
     this.capabilities = session.Capabilities.fromJSON(cmd.parameters);
 
     if (!this.secureTLS) {
       logger.warn("TLS certificate errors will be ignored for this session");
       let acceptAllCerts = new cert.InsecureSweepingOverride();