--- a/python/mozbuild/mozbuild/vendor/vendor_manifest.py
+++ b/python/mozbuild/mozbuild/vendor/vendor_manifest.py
@@ -332,24 +332,29 @@ class VendorManifest(MozbuildObject):
                     logging.INFO,
                     "vendor",
                     {"path": path},
                     "Performing delete-path action path: {path}",
                 )
                 mozfile.remove(path)
             elif update["action"] == "run-script":
                 script = get_full_path(update["script"], support_cwd=True)
-                run_dir = get_full_path(update["cwd"])
+                run_dir = get_full_path(update["cwd"], support_cwd=True)
                 self.log(
                     logging.INFO,
                     "vendor",
                     {"script": script, "run_dir": run_dir},
                     "Performing run-script action script: {script} working dir: {run_dir}",
                 )
-                self.run_process(args=[script], cwd=run_dir, log_name=script)
+                self.run_process(
+                    args=[script],
+                    cwd=run_dir,
+                    log_name=script,
+                    require_unix_environment=True,
+                )
             else:
                 assert False, "Unknown action supplied (how did this pass validation?)"
 
     def update_moz_build(self, vendoring_dir, moz_yaml_dir, add_to_exports):
         if vendoring_dir == moz_yaml_dir:
             vendoring_dir = moz_yaml_dir = None
 
         # If you edit this (especially for header files) you should double check