diff --git a/remote/shared/webdriver/Capabilities.sys.mjs b/remote/shared/webdriver/Capabilities.sys.mjs
index 0a418267847d..51eb30b80ae6 100644
--- a/remote/shared/webdriver/Capabilities.sys.mjs
+++ b/remote/shared/webdriver/Capabilities.sys.mjs
@@ -20,6 +20,19 @@ XPCOMUtils.defineLazyGetter(lazy, "remoteAgent", () => {
   return Cc["@mozilla.org/remote/agent;1"].createInstance(Ci.nsIRemoteAgent);
 });
 
+// List of capabilities which are only relevant for Webdriver Classic.
+export const WEBDRIVER_CLASSIC_CAPABILITIES = [
+  "pageLoadStrategy",
+  "timeouts",
+  "strictFileInteractability",
+  "unhandledPromptBehavior",
+  "webSocketUrl",
+  "moz:useNonSpecCompliantPointerOrigin",
+  "moz:webdriverClick",
+  "moz:debuggerAddress",
+  "moz:firefoxOptions",
+];
+
 /** Representation of WebDriver session timeouts. */
 export class Timeouts {
   constructor() {
@@ -515,13 +528,9 @@ export class Capabilities extends Map {
       lazy.pprint`Expected "capabilities" to be an object, got ${json}"`
     );
 
-    return Capabilities.match_(json);
-  }
-
-  // Matches capabilities as described by WebDriver.
-  static match_(json = {}) {
-    let matched = new Capabilities();
-
+    const capabilities = new Capabilities();
+    // TODO: Bug 1823907. We can start using here spec compliant method `validate`,
+    // as soon as `desiredCapabilities` and `requiredCapabilities` are not supported.
     for (let [k, v] of Object.entries(json)) {
       switch (k) {
         case "acceptInsecureCerts":
@@ -636,11 +645,152 @@ export class Capabilities extends Map {
           }
           break;
       }
-
-      matched.set(k, v);
+      capabilities.set(k, v);
     }
 
-    return matched;
+    return capabilities;
+  }
+
+  /**
+   * Validate WebDriver capability.
+   *
+   * @param {string} name
+   *    The name of capability.
+   * @param {string} value
+   *    The value of capability.
+   *
+   * @throws {InvalidArgumentError}
+   *   If <var>value</var> doesn't pass validation,
+   *   which depends on <var>name</var>.
+   *
+   * @returns {string}
+   *     The validated capability value.
+   */
+  static validate(name, value) {
+    if (value === null) {
+      return value;
+    }
+    switch (name) {
+      case "acceptInsecureCerts":
+        lazy.assert.boolean(
+          value,
+          lazy.pprint`Expected ${name} to be a boolean, got ${value}`
+        );
+        return value;
+
+      case "browserName":
+      case "browserVersion":
+      case "platformName":
+        return lazy.assert.string(
+          value,
+          lazy.pprint`Expected ${name} to be a string, got ${value}`
+        );
+
+      case "pageLoadStrategy":
+        lazy.assert.string(
+          value,
+          lazy.pprint`Expected ${name} to be a string, got ${value}`
+        );
+        if (!Object.values(PageLoadStrategy).includes(value)) {
+          throw new lazy.error.InvalidArgumentError(
+            "Unknown page load strategy: " + value
+          );
+        }
+        return value;
+
+      case "proxy":
+        return Proxy.fromJSON(value);
+
+      case "strictFileInteractability":
+        return lazy.assert.boolean(value);
+
+      case "timeouts":
+        return Timeouts.fromJSON(value);
+
+      case "unhandledPromptBehavior":
+        lazy.assert.string(
+          value,
+          lazy.pprint`Expected ${name} to be a string, got ${value}`
+        );
+        if (!Object.values(UnhandledPromptBehavior).includes(value)) {
+          throw new lazy.error.InvalidArgumentError(
+            `Unknown unhandled prompt behavior: ${value}`
+          );
+        }
+        return value;
+
+      case "webSocketUrl":
+        lazy.assert.boolean(
+          value,
+          lazy.pprint`Expected ${name} to be a boolean, got ${value}`
+        );
+
+        if (!value) {
+          throw new lazy.error.InvalidArgumentError(
+            lazy.pprint`Expected ${name} to be true, got ${value}`
+          );
+        }
+        return value;
+
+      case "moz:firefoxOptions":
+        return lazy.assert.object(
+          value,
+          lazy.pprint`Expected ${name} to be an object, got ${value}`
+        );
+
+      case "moz:accessibilityChecks":
+        return lazy.assert.boolean(
+          value,
+          lazy.pprint`Expected ${name} to be a boolean, got ${value}`
+        );
+
+      case "moz:useNonSpecCompliantPointerOrigin":
+        return lazy.assert.boolean(
+          value,
+          lazy.pprint`Expected ${name} to be a boolean, got ${value}`
+        );
+
+      case "moz:webdriverClick":
+        return lazy.assert.boolean(
+          value,
+          lazy.pprint`Expected ${name} to be a boolean, got ${value}`
+        );
+
+      case "moz:windowless":
+        lazy.assert.boolean(
+          value,
+          lazy.pprint`Expected ${name} to be a boolean, got ${value}`
+        );
+
+        // Only supported on MacOS
+        if (value && !lazy.AppInfo.isMac) {
+          throw new lazy.error.InvalidArgumentError(
+            "moz:windowless only supported on MacOS"
+          );
+        }
+        return value;
+
+      case "moz:debuggerAddress":
+        return lazy.assert.boolean(
+          value,
+          lazy.pprint`Expected ${name} to be a boolean, got ${value}`
+        );
+
+      default:
+        lazy.assert.string(
+          name,
+          lazy.pprint`Expected capability name to be a string, got ${name}`
+        );
+        if (name.includes(":")) {
+          const [prefix] = name.split(":");
+          if (prefix !== "moz") {
+            return value;
+          }
+        }
+        throw new lazy.error.InvalidArgumentError(
+          `${name} is not the name of a known capability or extension capability`
+        );
+    }
   }
 }
 
@@ -735,3 +885,125 @@ function maybeProfile() {
     return "<protected>";
   }
 }
+
+/**
+ * Merge WebDriver capabilities.
+ *
+ * @see https://w3c.github.io/webdriver/#dfn-merging-capabilities
+ *
+ * @param {object} primary
+ *     Required capabilities which need to be merged with <var>secondary</var>.
+ * @param {object=} secondary
+ *     Secondary capabilities.
+ *
+ * @returns {object} Merged capabilities.
+ *
+ * @throws {InvalidArgumentError}
+ *     If <var>primary</var> and <var>secondary</var> have the same keys.
+ */
+export function mergeCapabilities(primary, secondary) {
+  const result = { ...primary };
+
+  if (secondary === undefined) {
+    return result;
+  }
+
+  Object.entries(secondary).forEach(([name, value]) => {
+    if (primary[name] !== undefined) {
+      // Since at the moment we always pass as `primary` `alwaysMatch` object
+      // and as `secondary` an item from `firstMatch` array from `capabilities`,
+      // we can make this error message more specific.
+      throw new lazy.error.InvalidArgumentError(
+        `firstMatch key ${name} shadowed a value in alwaysMatch`
+      );
+    }
+    result[name] = value;
+  });
+
+  return result;
+}
+
+/**
+ * Validate WebDriver capabilities.
+ *
+ * @see https://w3c.github.io/webdriver/#dfn-validate-capabilities
+ *
+ * @param {object} capabilities
+ *     Capabilities which need to be validated.
+ *
+ * @returns {object} Validated capabilities.
+ *
+ * @throws {InvalidArgumentError}
+ *     If <var>capabilities</var> is not an object.
+ */
+export function validateCapabilities(capabilities) {
+  lazy.assert.object(capabilities);
+
+  const result = {};
+
+  Object.entries(capabilities).forEach(([name, value]) => {
+    const deserialized = Capabilities.validate(name, value);
+    if (deserialized !== null) {
+      if (name === "proxy" || name === "timeouts") {
+        // Return pure value, the Proxy and Timeouts objects will be setup
+        // during session creation.
+        result[name] = value;
+      } else {
+        result[name] = deserialized;
+      }
+    }
+  });
+
+  return result;
+}
+
+/**
+ * Process WebDriver capabilities.
+ *
+ * @see https://w3c.github.io/webdriver/#processing-capabilities
+ *
+ * @param {object} params
+ * @param {object} params.capabilities
+ *     Capabilities which need to be processed.
+ *
+ * @returns {object} Processed capabilities.
+ *
+ * @throws {InvalidArgumentError}
+ *     If <var>capabilities</var> do not satisfy the criteria.
+ */
+export function processCapabilities(params) {
+  const { capabilities } = params;
+  lazy.assert.object(capabilities);
+
+  let {
+    alwaysMatch: requiredCapabilities = {},
+    firstMatch: allFirstMatchCapabilities = [{}],
+  } = capabilities;
+
+  requiredCapabilities = validateCapabilities(requiredCapabilities);
+
+  lazy.assert.array(allFirstMatchCapabilities);
+  lazy.assert.that(
+    firstMatch => firstMatch.length >= 1,
+    lazy.pprint`Expected firstMatch ${allFirstMatchCapabilities} to have at least 1 entry`
+  )(allFirstMatchCapabilities);
+
+  const validatedFirstMatchCapabilities =
+    allFirstMatchCapabilities.map(validateCapabilities);
+
+  const mergedCapabilities = [];
+  validatedFirstMatchCapabilities.forEach(firstMatchCapabilities => {
+    const merged = mergeCapabilities(
+      requiredCapabilities,
+      firstMatchCapabilities
+    );
+    mergedCapabilities.push(merged);
+  });
+
+  // TODO: Bug 1836288. Implement the capability matching logic
+  // for "browserName", "browserVersion" and "platformName" features,
+  // for now we can just pick the first merged capability.
+  const matchedCapabilities = mergedCapabilities[0];
+
+  return matchedCapabilities;
+}
diff --git a/remote/shared/webdriver/test/xpcshell/test_Capabilities.js b/remote/shared/webdriver/test/xpcshell/test_Capabilities.js
index e88c0126c9d3..74e788e7a39e 100644
--- a/remote/shared/webdriver/test/xpcshell/test_Capabilities.js
+++ b/remote/shared/webdriver/test/xpcshell/test_Capabilities.js
@@ -16,10 +16,13 @@ const { error } = ChromeUtils.importESModule(
 );
 const {
   Capabilities,
+  mergeCapabilities,
   PageLoadStrategy,
+  processCapabilities,
   Proxy,
   Timeouts,
   UnhandledPromptBehavior,
+  validateCapabilities,
 } = ChromeUtils.importESModule(
   "chrome://remote/content/shared/webdriver/Capabilities.sys.mjs"
 );
@@ -439,9 +442,6 @@ add_task(function test_Capabilities_fromJSON() {
   for (let typ of [{}, null, undefined]) {
     ok(fromJSON(typ).has("browserName"));
   }
-  for (let typ of [true, 42, "foo", []]) {
-    Assert.throws(() => fromJSON(typ), /InvalidArgumentError/);
-  }
 
   // matching
   let caps = new Capabilities();
@@ -450,23 +450,11 @@ add_task(function test_Capabilities_fromJSON() {
   equal(true, caps.get("acceptInsecureCerts"));
   caps = fromJSON({ acceptInsecureCerts: false });
   equal(false, caps.get("acceptInsecureCerts"));
-  Assert.throws(
-    () => fromJSON({ acceptInsecureCerts: "foo" }),
-    /InvalidArgumentError/
-  );
 
   for (let strategy of Object.values(PageLoadStrategy)) {
     caps = fromJSON({ pageLoadStrategy: strategy });
     equal(strategy, caps.get("pageLoadStrategy"));
   }
-  Assert.throws(
-    () => fromJSON({ pageLoadStrategy: "foo" }),
-    /InvalidArgumentError/
-  );
-  Assert.throws(
-    () => fromJSON({ pageLoadStrategy: null }),
-    /InvalidArgumentError/
-  );
 
   let proxyConfig = { proxyType: "manual" };
   caps = fromJSON({ proxy: proxyConfig });
@@ -476,20 +464,6 @@ add_task(function test_Capabilities_fromJSON() {
   caps = fromJSON({ timeouts: timeoutsConfig });
   equal(123, caps.get("timeouts").implicit);
 
-  if (!AppInfo.isAndroid) {
-    caps = fromJSON({ setWindowRect: true });
-    equal(true, caps.get("setWindowRect"));
-    Assert.throws(
-      () => fromJSON({ setWindowRect: false }),
-      /InvalidArgumentError/
-    );
-  } else {
-    Assert.throws(
-      () => fromJSON({ setWindowRect: true }),
-      /InvalidArgumentError/
-    );
-  }
-
   caps = fromJSON({ strictFileInteractability: false });
   equal(false, caps.get("strictFileInteractability"));
   caps = fromJSON({ strictFileInteractability: true });
@@ -497,27 +471,11 @@ add_task(function test_Capabilities_fromJSON() {
 
   caps = fromJSON({ webSocketUrl: true });
   equal(true, caps.get("webSocketUrl"));
-  Assert.throws(
-    () => fromJSON({ webSocketUrl: false }),
-    /InvalidArgumentError/
-  );
-  Assert.throws(
-    () => fromJSON({ webSocketUrl: "foo" }),
-    /InvalidArgumentError/
-  );
 
   caps = fromJSON({ "moz:accessibilityChecks": true });
   equal(true, caps.get("moz:accessibilityChecks"));
   caps = fromJSON({ "moz:accessibilityChecks": false });
   equal(false, caps.get("moz:accessibilityChecks"));
-  Assert.throws(
-    () => fromJSON({ "moz:accessibilityChecks": "foo" }),
-    /InvalidArgumentError/
-  );
-  Assert.throws(
-    () => fromJSON({ "moz:accessibilityChecks": 1 }),
-    /InvalidArgumentError/
-  );
 
   // capability is always populated with null if remote agent is not listening
   caps = fromJSON({});
@@ -531,26 +489,137 @@ add_task(function test_Capabilities_fromJSON() {
   equal(false, caps.get("moz:useNonSpecCompliantPointerOrigin"));
   caps = fromJSON({ "moz:useNonSpecCompliantPointerOrigin": true });
   equal(true, caps.get("moz:useNonSpecCompliantPointerOrigin"));
-  Assert.throws(
-    () => fromJSON({ "moz:useNonSpecCompliantPointerOrigin": "foo" }),
-    /InvalidArgumentError/
-  );
-  Assert.throws(
-    () => fromJSON({ "moz:useNonSpecCompliantPointerOrigin": 1 }),
-    /InvalidArgumentError/
-  );
-
   caps = fromJSON({ "moz:webdriverClick": true });
   equal(true, caps.get("moz:webdriverClick"));
   caps = fromJSON({ "moz:webdriverClick": false });
   equal(false, caps.get("moz:webdriverClick"));
+});
+
+add_task(function test_mergeCapabilities() {
+  // Shadowed values.
   Assert.throws(
-    () => fromJSON({ "moz:webdriverClick": "foo" }),
+    () =>
+      mergeCapabilities(
+        { acceptInsecureCerts: true },
+        { acceptInsecureCerts: false }
+      ),
     /InvalidArgumentError/
   );
-  Assert.throws(
-    () => fromJSON({ "moz:webdriverClick": 1 }),
-    /InvalidArgumentError/
+
+  deepEqual(
+    { acceptInsecureCerts: true },
+    mergeCapabilities({ acceptInsecureCerts: true }, undefined)
+  );
+  deepEqual(
+    { acceptInsecureCerts: true, browserName: "Firefox" },
+    mergeCapabilities({ acceptInsecureCerts: true }, { browserName: "Firefox" })
+  );
+});
+
+add_task(function test_validateCapabilities_invalid() {
+  const invalidCapabilities = [
+    true,
+    42,
+    "foo",
+    [],
+    { acceptInsecureCerts: "foo" },
+    { browserName: true },
+    { browserVersion: true },
+    { platformName: true },
+    { pageLoadStrategy: "foo" },
+    { proxy: false },
+    { strictFileInteractability: "foo" },
+    { timeouts: false },
+    { unhandledPromptBehavior: false },
+    { webSocketUrl: false },
+    { webSocketUrl: "foo" },
+    { "moz:firefoxOptions": "foo" },
+    { "moz:accessibilityChecks": "foo" },
+    { "moz:useNonSpecCompliantPointerOrigin": "foo" },
+    { "moz:useNonSpecCompliantPointerOrigin": 1 },
+    { "moz:webdriverClick": "foo" },
+    { "moz:webdriverClick": 1 },
+    { "moz:debuggerAddress": "foo" },
+    { "moz:someRandomString": {} },
+  ];
+  for (const capabilities of invalidCapabilities) {
+    Assert.throws(
+      () => validateCapabilities(capabilities),
+      /InvalidArgumentError/
+    );
+  }
+});
+
+add_task(function test_validateCapabilities_valid() {
+  // Ignore null value.
+  deepEqual({}, validateCapabilities({ test: null }));
+
+  const validCapabilities = [
+    { acceptInsecureCerts: true },
+    { browserName: "firefox" },
+    { browserVersion: "12" },
+    { platformName: "linux" },
+    { pageLoadStrategy: "eager" },
+    { proxy: { proxyType: "manual", httpProxy: "test.com" } },
+    { strictFileInteractability: true },
+    { timeouts: { pageLoad: 500 } },
+    { unhandledPromptBehavior: "accept" },
+    { webSocketUrl: true },
+    { "moz:firefoxOptions": {} },
+    { "moz:accessibilityChecks": true },
+    { "moz:useNonSpecCompliantPointerOrigin": true },
+    { "moz:webdriverClick": true },
+    { "moz:debuggerAddress": true },
+    { "test:extension": "foo" },
+  ];
+  for (const validCapability of validCapabilities) {
+    deepEqual(validCapability, validateCapabilities(validCapability));
+  }
+});
+
+add_task(function test_processCapabilities() {
+  for (const invalidValue of [
+    { capabilities: null },
+    { capabilities: undefined },
+    { capabilities: "foo" },
+    { capabilities: true },
+    { capabilities: [] },
+    { capabilities: { alwaysMatch: null } },
+    { capabilities: { alwaysMatch: "foo" } },
+    { capabilities: { alwaysMatch: true } },
+    { capabilities: { alwaysMatch: [] } },
+    { capabilities: { firstMatch: null } },
+    { capabilities: { firstMatch: "foo" } },
+    { capabilities: { firstMatch: true } },
+    { capabilities: { firstMatch: {} } },
+    { capabilities: { firstMatch: [] } },
+  ]) {
+    Assert.throws(
+      () => processCapabilities(invalidValue),
+      /InvalidArgumentError/
+    );
+  }
+
+  deepEqual(
+    { acceptInsecureCerts: true },
+    processCapabilities({
+      capabilities: { alwaysMatch: { acceptInsecureCerts: true } },
+    })
+  );
+  deepEqual(
+    { browserName: "Firefox" },
+    processCapabilities({
+      capabilities: { firstMatch: [{ browserName: "Firefox" }] },
+    })
+  );
+  deepEqual(
+    { acceptInsecureCerts: true, browserName: "Firefox" },
+    processCapabilities({
+      capabilities: {
+        alwaysMatch: { acceptInsecureCerts: true },
+        firstMatch: [{ browserName: "Firefox" }],
+      },
+    })
   );
 });
 
diff --git a/remote/test/puppeteer/packages/puppeteer-core/src/common/bidi/Browser.ts b/remote/test/puppeteer/packages/puppeteer-core/src/common/bidi/Browser.ts
index 9741ce7129d5..0aa06c21382b 100644
--- a/remote/test/puppeteer/packages/puppeteer-core/src/common/bidi/Browser.ts
+++ b/remote/test/puppeteer/packages/puppeteer-core/src/common/bidi/Browser.ts
@@ -36,7 +36,7 @@ export class Browser extends BrowserBase {
   static async create(opts: Options): Promise<Browser> {
     // TODO: await until the connection is established.
     try {
-      await opts.connection.send('session.new', {});
+      await opts.connection.send('session.new', { capabilities: {}});
     } catch {}
     await opts.connection.send('session.subscribe', {
       events: [
diff --git a/remote/webdriver-bidi/WebDriverBiDiConnection.sys.mjs b/remote/webdriver-bidi/WebDriverBiDiConnection.sys.mjs
index 96482222b34d..e102a5086b82 100644
--- a/remote/webdriver-bidi/WebDriverBiDiConnection.sys.mjs
+++ b/remote/webdriver-bidi/WebDriverBiDiConnection.sys.mjs
@@ -12,7 +12,11 @@ ChromeUtils.defineESModuleGetters(lazy, {
   assert: "chrome://remote/content/shared/webdriver/Assert.sys.mjs",
   error: "chrome://remote/content/shared/webdriver/Errors.sys.mjs",
   Log: "chrome://remote/content/shared/Log.sys.mjs",
+  processCapabilities:
+    "chrome://remote/content/shared/webdriver/Capabilities.sys.mjs",
   RemoteAgent: "chrome://remote/content/components/RemoteAgent.sys.mjs",
+  WEBDRIVER_CLASSIC_CAPABILITIES:
+    "chrome://remote/content/shared/webdriver/Capabilities.sys.mjs",
 });
 
 XPCOMUtils.defineLazyGetter(lazy, "logger", () =>
@@ -156,11 +160,25 @@ export class WebDriverBiDiConnection extends WebSocketConnection {
 
       // Handle static commands first
       if (module === "session" && command === "new") {
-        // TODO: Needs capability matching code
+        const processedCapabilities = lazy.processCapabilities(params);
+
         result = await lazy.RemoteAgent.webDriverBiDi.createSession(
-          params,
+          processedCapabilities,
           this
         );
+
+        // Since in Capabilities class we setup default values also for capabilities which are
+        // not relevant for bidi, we want to remove them from the payload before returning to a client.
+        result.capabilities = Array.from(result.capabilities.entries()).reduce(
+          (object, [key, value]) => {
+            if (!lazy.WEBDRIVER_CLASSIC_CAPABILITIES.includes(key)) {
+              object[key] = value;
+            }
+
+            return object;
+          },
+          {}
+        );
       } else if (module === "session" && command === "status") {
         result = lazy.RemoteAgent.webDriverBiDi.getSessionReadinessStatus();
       } else {
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_capabilities.py b/testing/marionette/harness/marionette_harness/tests/unit/test_capabilities.py
index f78552ee121f..72de324f15f0 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_capabilities.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_capabilities.py
@@ -171,7 +171,7 @@ class TestCapabilityMatching(MarionetteTestCase):
 
         self.delete_session()
 
-        for value in ["", "EAGER", True, 42, {}, [], None]:
+        for value in ["", "EAGER", True, 42, {}, []]:
             print("invalid strategy {}".format(value))
             with self.assertRaisesRegexp(
                 SessionNotCreatedException, "InvalidArgumentError"
@@ -179,20 +179,10 @@ class TestCapabilityMatching(MarionetteTestCase):
                 self.marionette.start_session({"pageLoadStrategy": value})
 
     def test_set_window_rect(self):
-        if self.browser_name == "firefox":
-            self.marionette.start_session({"setWindowRect": True})
-            self.delete_session()
-            with self.assertRaisesRegexp(
-                SessionNotCreatedException, "InvalidArgumentError"
-            ):
-                self.marionette.start_session({"setWindowRect": False})
-        else:
+        with self.assertRaisesRegexp(
+            SessionNotCreatedException, "InvalidArgumentError"
+        ):
             self.marionette.start_session({"setWindowRect": False})
-            self.delete_session()
-            with self.assertRaisesRegexp(
-                SessionNotCreatedException, "InvalidArgumentError"
-            ):
-                self.marionette.start_session({"setWindowRect": True})
 
     def test_timeouts(self):
         for value in ["", 2.5, {}, []]:
@@ -260,7 +250,7 @@ class TestCapabilityMatching(MarionetteTestCase):
 
         # Invalid values
         self.delete_session()
-        for behavior in [None, "", "ACCEPT", True, 42, {}, []]:
+        for behavior in ["", "ACCEPT", True, 42, {}, []]:
             print("invalid unhandled prompt behavior {}".format(behavior))
             with self.assertRaisesRegexp(
                 SessionNotCreatedException, "InvalidArgumentError"
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_prefs_enforce.py b/testing/marionette/harness/marionette_harness/tests/unit/test_prefs_enforce.py
index 281bf806b841..609bed052778 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_prefs_enforce.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_prefs_enforce.py
@@ -48,7 +48,7 @@ class TestEnforcePreferences(MarionetteTestCase):
 
     def test_restart_preserves_requested_capabilities(self):
         self.marionette.delete_session()
-        self.marionette.start_session(capabilities={"moz:fooBar": True})
+        self.marionette.start_session(capabilities={"test:fooBar": True})
 
         self.enforce_prefs()
-        self.assertEqual(self.marionette.session.get("moz:fooBar"), True)
+        self.assertEqual(self.marionette.session.get("test:fooBar"), True)
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_quit_restart.py b/testing/marionette/harness/marionette_harness/tests/unit/test_quit_restart.py
index dc4bc71715f9..f41b374896be 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_quit_restart.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_quit_restart.py
@@ -190,10 +190,10 @@ class TestQuitRestart(MarionetteTestCase):
 
     def test_restart_preserves_requested_capabilities(self):
         self.marionette.delete_session()
-        self.marionette.start_session(capabilities={"moz:fooBar": True})
+        self.marionette.start_session(capabilities={"test:fooBar": True})
 
         self.marionette.restart(in_app=False)
-        self.assertEqual(self.marionette.session.get("moz:fooBar"), True)
+        self.assertEqual(self.marionette.session.get("test:fooBar"), True)
 
     def test_restart_safe_mode(self):
         try:
@@ -304,11 +304,11 @@ class TestQuitRestart(MarionetteTestCase):
 
     def test_in_app_restart_preserves_requested_capabilities(self):
         self.marionette.delete_session()
-        self.marionette.start_session(capabilities={"moz:fooBar": True})
+        self.marionette.start_session(capabilities={"test:fooBar": True})
 
         details = self.marionette.restart()
         self.assertTrue(details["in_app"], "Expected in_app restart")
-        self.assertEqual(self.marionette.session.get("moz:fooBar"), True)
+        self.assertEqual(self.marionette.session.get("test:fooBar"), True)
 
     @unittest.skipUnless(sys.platform.startswith("darwin"), "Only supported on MacOS")
     def test_in_app_silent_restart_fails_without_windowless_flag_on_mac_os(self):