diff --git a/bin/_mocha b/bin/_mocha
index 9004ca763b..ad4ed40373 100755
--- a/bin/_mocha
+++ b/bin/_mocha
@@ -83,6 +83,7 @@ program
   .option('--globals <names>', 'allow the given comma-delimited global [names]', list, [])
   .option('--es_staging', 'enable all staged features')
   .option('--harmony<_classes,_generators,...>', 'all node --harmony* flags are available')
+  .option('--icu-data-dir', 'include ICU data')
   .option('--inline-diffs', 'display actual/expected differences inline within each string')
   .option('--interfaces', 'display available interfaces')
   .option('--no-deprecation', 'silence deprecation warnings')
diff --git a/bin/mocha b/bin/mocha
index 3a392379d0..f6606e49b5 100755
--- a/bin/mocha
+++ b/bin/mocha
@@ -48,6 +48,7 @@ process.argv.slice(2).forEach(function(arg){
     default:
       if (0 == arg.indexOf('--harmony')) args.unshift(arg);
       else if (0 == arg.indexOf('--trace')) args.unshift(arg);
+      else if (0 == arg.indexOf('--icu-data-dir')) args.unshift(arg);
       else if (0 == arg.indexOf('--max-old-space-size')) args.unshift(arg);
       else args.push(arg);
       break;