diff --git a/tools_webrtc/mb/mb.py b/tools_webrtc/mb/mb.py
index 4db1bc3..f18a059 100755
--- a/tools_webrtc/mb/mb.py
+++ b/tools_webrtc/mb/mb.py
@@ -1048,7 +1048,7 @@
                                 % (target, test_type), output_path=None)
 
     cmdline = []
-    extra_files = []
+    extra_files = ['../../.vpython']
 
     if test_type == 'script':
       cmdline = ['../../' + self.ToSrcRelPath(isolate_map[target]['script'])]
diff --git a/tools_webrtc/mb/mb_unittest.py b/tools_webrtc/mb/mb_unittest.py
index 7c1f1e6..5b41644 100755
--- a/tools_webrtc/mb/mb_unittest.py
+++ b/tools_webrtc/mb/mb_unittest.py
@@ -376,7 +376,7 @@
     files = isolate_file_contents['variables']['files']
     command = isolate_file_contents['variables']['command']
 
-    self.assertEqual(files, ['base_unittests'])
+    self.assertEqual(files, ['../../.vpython', 'base_unittests'])
     self.assertEqual(command, [
         '../../build/android/test_wrapper/logdog_wrapper.py',
         '--target', 'base_unittests',
@@ -409,7 +409,7 @@
     files = isolate_file_contents['variables']['files']
     command = isolate_file_contents['variables']['command']
 
-    self.assertEqual(files, ['base_unittests'])
+    self.assertEqual(files, ['../../.vpython', 'base_unittests'])
     self.assertEqual(command, [
         '../../build/android/test_wrapper/logdog_wrapper.py',
         '--target', 'base_unittests',
@@ -494,6 +494,7 @@
     command = isolate_file_contents['variables']['command']
 
     self.assertEqual(files, [
+        '../../.vpython',
         'base_unittests',
         'base_unittests_script.py',
     ])