diff --git a/lib/cli.ts b/lib/cli.ts
index f1d6cee75..4bf0b78d0 100644
--- a/lib/cli.ts
+++ b/lib/cli.ts
@@ -175,18 +175,10 @@ if (argv.version) {
   process.exit(0);
 }
 
-if (!argv.disableChecks) {
-  // Check to see if additional flags were used.
-  let unknownKeys: string[] = Object.keys(argv).filter((element: string) => {
-    return element !== '$0' && element !== '_' && allowedNames.indexOf(element) === -1;
-  });
-
-  if (unknownKeys.length > 0) {
-    throw new Error(
-        'Found extra flags: ' + unknownKeys.join(', ') +
-        ', please use --disableChecks flag to disable the Protractor CLI flag checks.');
-  }
-}
+// Check to see if additional flags were used.
+argv.unknownFlags_ = Object.keys(argv).filter((element: string) => {
+  return element !== '$0' && element !== '_' && allowedNames.indexOf(element) === -1;
+});
 
 /**
  * Helper to resolve comma separated lists of file pattern strings relative to
diff --git a/lib/config.ts b/lib/config.ts
index d274bdd18..d4dee0c2c 100644
--- a/lib/config.ts
+++ b/lib/config.ts
@@ -595,7 +595,13 @@ export interface Config {
    */
   ng12Hybrid?: boolean;
 
-  seleniumArgs?: Array<any>;
+  /**
+   * Protractor will exit with an error if it sees any command line flags it doesn't
+   * recognize. Set disableChecks true to disable this check.
+   */
+  disableChecks?: boolean;
+
+  seleniumArgs?: any[];
   jvmArgs?: string[];
   configDir?: string;
   troubleshoot?: boolean;
@@ -607,4 +613,5 @@ export interface Config {
   frameworkPath?: string;
   elementExplorer?: any;
   debug?: boolean;
+  unknownFlags_?: string[];
 }
diff --git a/lib/frameworks/README.md b/lib/frameworks/README.md
index a0efc6f2f..1cbd8fa5b 100644
--- a/lib/frameworks/README.md
+++ b/lib/frameworks/README.md
@@ -37,7 +37,8 @@ Requirements
 
 - `runner.runTestPreparer` must be called after the framework has been
   initialized but before any spec files are run.  This function returns a
-  promise which should be waited on before executing tests.
+  promise which should be waited on before executing tests. The framework should
+  also pass an array of extra command line flags it accepts, if any.
 
 - `runner.getConfig().onComplete` must be called when tests are finished.
   It might return a promise, in which case `exports.run`'s promise should not
diff --git a/lib/runner.ts b/lib/runner.ts
index 983e17338..d38715b06 100644
--- a/lib/runner.ts
+++ b/lib/runner.ts
@@ -6,6 +6,7 @@ import * as util from 'util';
 import {ProtractorBrowser} from './browser';
 import {Config} from './config';
 import {buildDriverProvider, DriverProvider} from './driverProviders';
+import {ConfigError} from './exitCodes';
 import {Logger} from './logger';
 import {Plugins} from './plugins';
 import {protractor} from './ptor';
@@ -79,10 +80,21 @@ export class Runner extends EventEmitter {
   /**
    * Executor of testPreparer
    * @public
+   * @param {string[]=} An optional list of command line arguments the framework will accept.
    * @return {q.Promise} A promise that will resolve when the test preparers
    *     are finished.
    */
-  runTestPreparer(): q.Promise<any> {
+  runTestPreparer(extraFlags?: string[]): q.Promise<any> {
+    let unknownFlags = this.config_.unknownFlags_ || [];
+    if (extraFlags) {
+      unknownFlags = unknownFlags.filter((f) => extraFlags.indexOf(f) === -1);
+    }
+    if (unknownFlags.length > 0 && !this.config_.disableChecks) {
+      throw new ConfigError(
+          logger,
+          'Found extra flags: ' + unknownFlags.join(', ') +
+              ', please use --disableChecks flag to disable the Protractor CLI flag checks. ');
+    }
     return this.plugins_.onPrepare().then(() => {
       return helper.runFilenameOrFn_(this.config_.configDir, this.preparer_);
     });
diff --git a/scripts/errorTest.js b/scripts/errorTest.js
index 7a86f1bf6..6e55dcad2 100644
--- a/scripts/errorTest.js
+++ b/scripts/errorTest.js
@@ -21,7 +21,7 @@ var checkLogs = function(output, messages) {
 
 runProtractor = spawn('node',
     ['bin/protractor', 'example/conf.js', '--foobar', 'foobar']);
-output = runProtractor.stderr.toString();
+output = runProtractor.stdout.toString();
 messages = ['Error: Found extra flags: foobar'];
 checkLogs(output, messages);