diff --git a/testing/web-platform/mach_commands.py b/testing/web-platform/mach_commands.py
index ac54da72ea8c..3f5d9fb1232b 100644
--- a/testing/web-platform/mach_commands.py
+++ b/testing/web-platform/mach_commands.py
@@ -205,6 +205,10 @@ testing/web-platform/tests for tests that may be shared
                 template += self.template_body_reftest_wait
         else:
             template += self.template_body_th
+        try:
+            os.makedirs(os.path.dirname(path))
+        except OSError:
+            pass
         with open(path, "w") as f:
             f.write(template)