--- a/python/mozbuild/mozbuild/vendor_rust.py
+++ b/python/mozbuild/mozbuild/vendor_rust.py
@@ -264,16 +264,17 @@ license file's hash.
         self.log(logging.INFO, 'rm_vendor_dir', {}, 'rm -rf %s' % vendor_dir)
         mozfile.remove(vendor_dir)
         # Once we require a new enough cargo to switch to workspaces, we can
         # just do this once on the workspace root crate.
         crates_and_roots = (
             ('gkrust', 'toolkit/library/rust'),
             ('gkrust-gtest', 'toolkit/library/gtest/rust'),
             ('js', 'js/rust'),
+            ('mozjs_sys', 'js/src'),
             ('webdriver', 'testing/webdriver'),
             ('geckodriver', 'testing/geckodriver'),
         )
 
         lockfiles = []
         for (lib, crate_root) in crates_and_roots:
             path = mozpath.join(self.topsrcdir, crate_root)
             # We use check_call instead of mozprocess to ensure errors are displayed.