--- a/testing/geckodriver/src/marionette.rs
+++ b/testing/geckodriver/src/marionette.rs
@@ -979,31 +979,31 @@ impl MarionetteCommand {
                 legacy_caps.insert("desiredCapabilities".to_string(), caps.to_json());
                 data.insert("capabilities".to_string(), legacy_caps.to_json());
 
                 (Some("newSession"), Some(Ok(data)))
             },
             DeleteSession => {
                 let mut body = BTreeMap::new();
                 body.insert("flags".to_owned(), vec!["eForceQuit".to_json()].to_json());
-                (Some("quitApplication"), Some(Ok(body)))
+                (Some("quit"), Some(Ok(body)))
             },
             Status => panic!("Got status command that should already have been handled"),
             Get(ref x) => (Some("get"), Some(x.to_marionette())),
             GetCurrentUrl => (Some("getCurrentUrl"), None),
             GoBack => (Some("goBack"), None),
             GoForward => (Some("goForward"), None),
             Refresh => (Some("refresh"), None),
             GetTitle => (Some("getTitle"), None),
             GetPageSource => (Some("getPageSource"), None),
             GetWindowHandle => (Some("getWindowHandle"), None),
             GetWindowHandles => (Some("getWindowHandles"), None),
             CloseWindow => (Some("close"), None),
             GetTimeouts => (Some("getTimeouts"), None),
-            SetTimeouts(ref x) => (Some("timeouts"), Some(x.to_marionette())),
+            SetTimeouts(ref x) => (Some("setTimeouts"), Some(x.to_marionette())),
             SetWindowRect(ref x) => (Some("setWindowRect"), Some(x.to_marionette())),
             GetWindowRect => (Some("getWindowRect"), None),
             MaximizeWindow => (Some("maximizeWindow"), None),
             FullscreenWindow => (Some("fullscreenWindow"), None),
             SwitchToWindow(ref x) => (Some("switchToWindow"), Some(x.to_marionette())),
             SwitchToFrame(ref x) => (Some("switchToFrame"), Some(x.to_marionette())),
             SwitchToParentFrame => (Some("switchToParentFrame"), None),
             FindElement(ref x) => (Some("findElement"), Some(x.to_marionette())),

--- a/testing/marionette/client/marionette_driver/marionette.py
+++ b/testing/marionette/client/marionette_driver/marionette.py
@@ -1054,19 +1054,17 @@ class Marionette(object):
             if canceled:
                 raise errors.MarionetteException(
                     "Something cancelled the quit application request")
 
         body = None
         if len(flags) > 0:
             body = {"flags": list(flags)}
 
-        # quitApplication was renamed quit in bug 1337743,
-        # and this can safely be renamed when Firefox 56 becomes stable
-        self._send_message("quitApplication", body)
+        self._send_message("quit", body)
 
     @do_process_check
     def quit(self, clean=False, in_app=False, callback=None):
         """Terminate the currently running instance.
 
         This command will delete the active marionette session. It also allows
         manipulation of eg. the profile data while the application is not running.
         To start the application again, :func:`start_session` has to be called.

--- a/testing/marionette/client/marionette_driver/timeout.py
+++ b/testing/marionette/client/marionette_driver/timeout.py
@@ -24,21 +24,17 @@ class Timeouts(object):
 
     """
 
     def __init__(self, marionette):
         self._marionette = marionette
 
     def _set(self, name, sec):
         ms = sec * 1000
-        try:
-            self._marionette._send_message("setTimeouts", {name: ms})
-        except errors.UnknownCommandException:
-            # remove when 55 is stable
-            self._marionette._send_message("timeouts", {"type": name, "ms": ms})
+        self._marionette._send_message("setTimeouts", {name: ms})
 
     def _get(self, name):
         ts = self._marionette._send_message("getTimeouts")
         if name not in ts:
             raise KeyError()
         ms = ts[name]
         return ms / 1000
 

--- a/testing/marionette/driver.js
+++ b/testing/marionette/driver.js
@@ -1667,30 +1667,18 @@ GeckoDriver.prototype.getTimeouts = func
  *     Dictionary of timeout types and their new value, where all timeout
  *     types are optional.
  *
  * @throws {InvalidArgumentError}
  *     If timeout type key is unknown, or the value provided with it is
  *     not an integer.
  */
 GeckoDriver.prototype.setTimeouts = function (cmd, resp) {
-  // backwards compatibility with old API
-  // that accepted a dictionary {type: <string>, ms: <number>}
-  let json = {};
-  if (typeof cmd.parameters == "object" &&
-      "type" in cmd.parameters &&
-      "ms" in cmd.parameters) {
-    logger.warn("Using deprecated data structure for setting timeouts");
-    json = {[cmd.parameters.type]: parseInt(cmd.parameters.ms)};
-  } else {
-    json = cmd.parameters;
-  }
-
   // merge with existing timeouts
-  let merged = Object.assign(this.timeouts.toJSON(), json);
+  let merged = Object.assign(this.timeouts.toJSON(), cmd.parameters);
   this.timeouts = session.Timeouts.fromJSON(merged);
 };
 
 /** Single tap. */
 GeckoDriver.prototype.singleTap = function*(cmd, resp) {
   assert.window(this.getCurrentWindow());
 
   let {id, x, y} = cmd.parameters;
@@ -3198,17 +3186,16 @@ GeckoDriver.prototype.localizeProperty =
 
 GeckoDriver.prototype.commands = {
   "newSession": GeckoDriver.prototype.newSession,
   "getSessionCapabilities": GeckoDriver.prototype.getSessionCapabilities,
   "setContext": GeckoDriver.prototype.setContext,
   "getContext": GeckoDriver.prototype.getContext,
   "executeScript": GeckoDriver.prototype.executeScript,
   "getTimeouts": GeckoDriver.prototype.getTimeouts,
-  "timeouts": GeckoDriver.prototype.setTimeouts,  // deprecated until Firefox 55
   "setTimeouts": GeckoDriver.prototype.setTimeouts,
   "singleTap": GeckoDriver.prototype.singleTap,
   "performActions": GeckoDriver.prototype.performActions,
   "releaseActions": GeckoDriver.prototype.releaseActions,
   "actionChain": GeckoDriver.prototype.actionChain, // deprecated
   "multiAction": GeckoDriver.prototype.multiAction, // deprecated
   "executeAsyncScript": GeckoDriver.prototype.executeAsyncScript,
   "executeJSScript": GeckoDriver.prototype.executeJSScript,
@@ -3264,17 +3251,16 @@ GeckoDriver.prototype.commands = {
   "setWindowSize": GeckoDriver.prototype.setWindowRect, // Redirecting for compatibility
   "maximizeWindow": GeckoDriver.prototype.maximizeWindow,
   "fullscreen": GeckoDriver.prototype.fullscreen,
   "dismissDialog": GeckoDriver.prototype.dismissDialog,
   "acceptDialog": GeckoDriver.prototype.acceptDialog,
   "getTextFromDialog": GeckoDriver.prototype.getTextFromDialog,
   "sendKeysToDialog": GeckoDriver.prototype.sendKeysToDialog,
   "acceptConnections": GeckoDriver.prototype.acceptConnections,
-  "quitApplication": GeckoDriver.prototype.quit,  // deprecated, can be removed in Firefox 56
   "quit": GeckoDriver.prototype.quit,
 
   "localization:l10n:localizeEntity": GeckoDriver.prototype.localizeEntity,
   "localization:l10n:localizeProperty": GeckoDriver.prototype.localizeProperty,
 
   "addon:install": GeckoDriver.prototype.installAddon,
   "addon:uninstall": GeckoDriver.prototype.uninstallAddon,
 };

--- a/testing/marionette/harness/marionette_harness/tests/unit/test_timeouts.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_timeouts.py
@@ -92,27 +92,16 @@ class TestTimeouts(MarionetteTestCase):
         test_html = self.marionette.absolute_url("test.html")
         self.marionette.navigate(test_html)
         self.marionette.timeout.script = 1
         self.assertTrue(self.marionette.execute_async_script("""
              var callback = arguments[arguments.length - 1];
              setTimeout(function() { callback(true); }, 500);
              """))
 
-    def test_compat_input_types(self):
-        # When using the spec-incompatible input format which we have
-        # for backwards compatibility, it should be possible to send ms
-        # as a string type and have the server parseInt it to an integer.
-        body = {"type": "script", "ms": "30000"}
-        self.marionette._send_message("setTimeouts", body)
-
-    def test_deprecated_set_timeouts_command(self):
-        body = {"implicit": 3000}
-        self.marionette._send_message("timeouts", body)
-
     def test_deprecated_set_search_timeout(self):
         self.marionette.set_search_timeout(1000)
         self.assertEqual(1, self.marionette.timeout.implicit)
 
     def test_deprecated_set_script_timeout(self):
         self.marionette.set_script_timeout(2000)
         self.assertEqual(2, self.marionette.timeout.script)