diff --git a/testing/marionette/client/marionette/tests/unit/test_capabilities.py b/testing/marionette/client/marionette/tests/unit/test_capabilities.py
index baa74c0f3a4f..ddc6b4ccb4ca 100644
--- a/testing/marionette/client/marionette/tests/unit/test_capabilities.py
+++ b/testing/marionette/client/marionette/tests/unit/test_capabilities.py
@@ -18,6 +18,7 @@ class TestCapabilities(MarionetteTestCase):
         self.assertIn("browserVersion", self.caps)
         self.assertIn("platformName", self.caps)
         self.assertIn("platformVersion", self.caps)
+        self.assertIn("specificationLevel", self.caps)
 
         self.assertEqual(self.caps["browserName"], self.appinfo["name"])
         self.assertEqual(self.caps["browserVersion"], self.appinfo["version"])
diff --git a/testing/marionette/driver.js b/testing/marionette/driver.js
index f29bdd301fac..9f9159fe62b2 100644
--- a/testing/marionette/driver.js
+++ b/testing/marionette/driver.js
@@ -141,6 +141,7 @@ this.GeckoDriver = function(appName, device, emulator) {
     "browserVersion": Services.appinfo.version,
     "platformName": Services.appinfo.OS.toUpperCase(),
     "platformVersion": Services.appinfo.platformVersion,
+    "specificationLevel": "1",
 
     // Supported features
     "raisesAccessibilityExceptions": false,