diff --git a/browser/components/extensions/test/browser/browser_ext_devtools_inspectedWindow_eval_bindings.js b/browser/components/extensions/test/browser/browser_ext_devtools_inspectedWindow_eval_bindings.js
index 25f44103f1fa..570f36711419 100644
--- a/browser/components/extensions/test/browser/browser_ext_devtools_inspectedWindow_eval_bindings.js
+++ b/browser/components/extensions/test/browser/browser_ext_devtools_inspectedWindow_eval_bindings.js
@@ -126,7 +126,7 @@ add_task(async function test_devtools_inspectedWindow_eval_bindings() {
     if (jsterm.hud.NEW_CONSOLE_OUTPUT_ENABLED === true) {
       // Wait for the message to appear on the console.
       const messageNode = await new Promise(resolve => {
-        jsterm.hud.on("new-messages", function onThisMessage(e, messages) {
+        jsterm.hud.on("new-messages", function onThisMessage(messages) {
           for (let m of messages) {
             resolve(m.node);
             jsterm.hud.off("new-messages", onThisMessage);
@@ -166,7 +166,7 @@ add_task(async function test_devtools_inspectedWindow_eval_bindings() {
       is(nodes.length, 3, "The object preview has the expected number of nodes");
     } else {
       const options = await new Promise(resolve => {
-        jsterm.once("variablesview-open", (evt, view, options) => resolve(options));
+        jsterm.once("variablesview-open", (view, options) => resolve(options));
       });
 
       const objectType = options.objectActor.type;
diff --git a/devtools/client/scratchpad/test/browser_scratchpad_wrong_window_focus.js b/devtools/client/scratchpad/test/browser_scratchpad_wrong_window_focus.js
index b86ba758473f..6bd7868442ec 100644
--- a/devtools/client/scratchpad/test/browser_scratchpad_wrong_window_focus.js
+++ b/devtools/client/scratchpad/test/browser_scratchpad_wrong_window_focus.js
@@ -49,7 +49,7 @@ function test()
 function testFocus(sw, hud) {
   let sp = sw.Scratchpad;
 
-  function onMessage(event, messages) {
+  function onMessage(messages) {
     let msg = [...messages][0];
     let node = msg.node;
 
diff --git a/devtools/client/webconsole/jsterm.js b/devtools/client/webconsole/jsterm.js
index 9115c79c2624..4091a54deef5 100644
--- a/devtools/client/webconsole/jsterm.js
+++ b/devtools/client/webconsole/jsterm.js
@@ -16,7 +16,7 @@ const {KeyCodes} = require("devtools/client/shared/keycodes");
 loader.lazyServiceGetter(this, "clipboardHelper",
                          "@mozilla.org/widget/clipboardhelper;1",
                          "nsIClipboardHelper");
-loader.lazyRequireGetter(this, "EventEmitter", "devtools/shared/old-event-emitter");
+loader.lazyRequireGetter(this, "EventEmitter", "devtools/shared/event-emitter");
 loader.lazyRequireGetter(this, "AutocompletePopup", "devtools/client/shared/autocomplete-popup");
 loader.lazyRequireGetter(this, "ToolSidebar", "devtools/client/framework/sidebar", true);
 loader.lazyRequireGetter(this, "Messages", "devtools/client/webconsole/console-output", true);
@@ -639,7 +639,7 @@ JSTerm.prototype = {
         window.focus();
       }
 
-      this.emit("variablesview-open", view, options);
+      this.emit("variablesview-open", {view, options});
       return view;
     };
 
diff --git a/devtools/client/webconsole/new-console-output/new-console-output-wrapper.js b/devtools/client/webconsole/new-console-output/new-console-output-wrapper.js
index 10ee1373ad19..7a886de48671 100644
--- a/devtools/client/webconsole/new-console-output/new-console-output-wrapper.js
+++ b/devtools/client/webconsole/new-console-output/new-console-output-wrapper.js
@@ -12,7 +12,7 @@ const actions = require("devtools/client/webconsole/new-console-output/actions/i
 const { createContextMenu } = require("devtools/client/webconsole/new-console-output/utils/context-menu");
 const { configureStore } = require("devtools/client/webconsole/new-console-output/store");
 
-const EventEmitter = require("devtools/shared/old-event-emitter");
+const EventEmitter = require("devtools/shared/event-emitter");
 const ConsoleOutput = createFactory(require("devtools/client/webconsole/new-console-output/components/ConsoleOutput"));
 const FilterBar = createFactory(require("devtools/client/webconsole/new-console-output/components/FilterBar"));
 const SideBar = createFactory(require("devtools/client/webconsole/new-console-output/components/SideBar"));
@@ -241,7 +241,7 @@ NewConsoleOutputWrapper.prototype = {
 
       promise = new Promise(resolve => {
         let jsterm = this.jsterm;
-        jsterm.hud.on("new-messages", function onThisMessage(e, messages) {
+        jsterm.hud.on("new-messages", function onThisMessage(messages) {
           for (let m of messages) {
             if (m.timeStamp === timeStampToMatch) {
               resolve(m.node);
diff --git a/devtools/client/webconsole/new-console-output/test/chrome/test_render_perf.html b/devtools/client/webconsole/new-console-output/test/chrome/test_render_perf.html
index ac1d8e9e8a53..f6d8e30a6773 100644
--- a/devtools/client/webconsole/new-console-output/test/chrome/test_render_perf.html
+++ b/devtools/client/webconsole/new-console-output/test/chrome/test_render_perf.html
@@ -28,7 +28,7 @@ const NewConsoleOutputWrapper = browserRequire(
   "devtools/client/webconsole/new-console-output/new-console-output-wrapper");
 const actions =
   browserRequire("devtools/client/webconsole/new-console-output/actions/index");
-const EventEmitter = browserRequire("devtools/shared/old-event-emitter");
+const EventEmitter = browserRequire("devtools/shared/event-emitter");
 const testPackets = Array.from({length: NUM_MESSAGES}).map((el, id) => ({
   "from": "server1.conn4.child1/consoleActor2",
   "type": "consoleAPICall",
diff --git a/devtools/client/webconsole/new-console-output/test/fixtures/stub-generators/head.js b/devtools/client/webconsole/new-console-output/test/fixtures/stub-generators/head.js
index 6671a8acb123..78b6411e238c 100644
--- a/devtools/client/webconsole/new-console-output/test/fixtures/stub-generators/head.js
+++ b/devtools/client/webconsole/new-console-output/test/fixtures/stub-generators/head.js
@@ -437,7 +437,7 @@ function* generateNetworkEventStubs() {
 
     let onNetworkUpdate = new Promise(resolve => {
       let i = 0;
-      ui.jsterm.hud.on("network-message-updated", function onNetworkUpdated(event, res) {
+      ui.jsterm.hud.on("network-message-updated", function onNetworkUpdated(res) {
         let updateKey = `${keys[i++]} update`;
         // We cannot ensure the form of the network update packet, some properties
         // might be in another order than in the original packet.
diff --git a/devtools/client/webconsole/new-console-output/test/mochitest/browser_console_consolejsm_output.js b/devtools/client/webconsole/new-console-output/test/mochitest/browser_console_consolejsm_output.js
index 815d6dee3225..4532cae7637e 100644
--- a/devtools/client/webconsole/new-console-output/test/mochitest/browser_console_consolejsm_output.js
+++ b/devtools/client/webconsole/new-console-output/test/mochitest/browser_console_consolejsm_output.js
@@ -7,7 +7,7 @@
 
 "use strict";
 
-function onNewMessage(aEvent, aNewMessages) {
+function onNewMessage(aNewMessages) {
   for (let msg of aNewMessages) {
     // Messages that shouldn't be output contain the substring FAIL_TEST
     if (msg.node.textContent.includes("FAIL_TEST")) {
@@ -119,7 +119,7 @@ add_task(function* () {
 
   let deferred = defer();
 
-  let onFetch = (aEvent, aVar) => {
+  let onFetch = (aVar) => {
     // Skip the notification from console.dir variablesview-fetched.
     if (aVar._variablesView != hud.jsterm._variablesView) {
       return;
diff --git a/devtools/client/webconsole/new-console-output/test/mochitest/browser_webconsole_closure_inspection.js b/devtools/client/webconsole/new-console-output/test/mochitest/browser_webconsole_closure_inspection.js
index 7dc506554644..4de3682cab28 100644
--- a/devtools/client/webconsole/new-console-output/test/mochitest/browser_webconsole_closure_inspection.js
+++ b/devtools/client/webconsole/new-console-output/test/mochitest/browser_webconsole_closure_inspection.js
@@ -81,7 +81,7 @@ function onExecuteGetName(results) {
   });
 }
 
-function onGetNameFetch(evt, view) {
+function onGetNameFetch(view) {
   gVariablesView = view._variablesView;
   ok(gVariablesView, "variables view object");
 
diff --git a/devtools/client/webconsole/new-console-output/test/mochitest/head.js b/devtools/client/webconsole/new-console-output/test/mochitest/head.js
index 362a565970eb..cb40b911a191 100644
--- a/devtools/client/webconsole/new-console-output/test/mochitest/head.js
+++ b/devtools/client/webconsole/new-console-output/test/mochitest/head.js
@@ -108,7 +108,7 @@ function waitForMessages({ hud, messages }) {
   return new Promise(resolve => {
     const matchedMessages = [];
     hud.ui.on("new-messages",
-      function messagesReceived(e, newMessages) {
+      function messagesReceived(newMessages) {
         for (let message of messages) {
           if (message.matched) {
             continue;
diff --git a/devtools/client/webconsole/new-webconsole.js b/devtools/client/webconsole/new-webconsole.js
index a20455b601bc..e96834ebb73c 100644
--- a/devtools/client/webconsole/new-webconsole.js
+++ b/devtools/client/webconsole/new-webconsole.js
@@ -7,7 +7,7 @@
 "use strict";
 
 const {Utils: WebConsoleUtils} = require("devtools/client/webconsole/utils");
-const EventEmitter = require("devtools/shared/old-event-emitter");
+const EventEmitter = require("devtools/shared/event-emitter");
 const promise = require("promise");
 const defer = require("devtools/shared/defer");
 const Services = require("Services");
diff --git a/devtools/client/webconsole/panel.js b/devtools/client/webconsole/panel.js
index f149ff53fb7b..05e281e959a6 100644
--- a/devtools/client/webconsole/panel.js
+++ b/devtools/client/webconsole/panel.js
@@ -10,7 +10,7 @@ const promise = require("promise");
 const defer = require("devtools/shared/defer");
 
 loader.lazyRequireGetter(this, "HUDService", "devtools/client/webconsole/hudservice", true);
-loader.lazyGetter(this, "EventEmitter", () => require("devtools/shared/old-event-emitter"));
+loader.lazyGetter(this, "EventEmitter", () => require("devtools/shared/event-emitter"));
 
 /**
  * A DevToolPanel that controls the Web Console.
diff --git a/devtools/client/webconsole/test/browser_console_consolejsm_output.js b/devtools/client/webconsole/test/browser_console_consolejsm_output.js
index 815d6dee3225..4532cae7637e 100644
--- a/devtools/client/webconsole/test/browser_console_consolejsm_output.js
+++ b/devtools/client/webconsole/test/browser_console_consolejsm_output.js
@@ -7,7 +7,7 @@
 
 "use strict";
 
-function onNewMessage(aEvent, aNewMessages) {
+function onNewMessage(aNewMessages) {
   for (let msg of aNewMessages) {
     // Messages that shouldn't be output contain the substring FAIL_TEST
     if (msg.node.textContent.includes("FAIL_TEST")) {
@@ -119,7 +119,7 @@ add_task(function* () {
 
   let deferred = defer();
 
-  let onFetch = (aEvent, aVar) => {
+  let onFetch = (aVar) => {
     // Skip the notification from console.dir variablesview-fetched.
     if (aVar._variablesView != hud.jsterm._variablesView) {
       return;
diff --git a/devtools/client/webconsole/test/browser_console_hide_jsterm_when_devtools_chrome_enabled_false.js b/devtools/client/webconsole/test/browser_console_hide_jsterm_when_devtools_chrome_enabled_false.js
index 2bf28e39de84..345ecdf96409 100644
--- a/devtools/client/webconsole/test/browser_console_hide_jsterm_when_devtools_chrome_enabled_false.js
+++ b/devtools/client/webconsole/test/browser_console_hide_jsterm_when_devtools_chrome_enabled_false.js
@@ -28,7 +28,7 @@ function testObjectInspectorPropertiesAreNotSet(variablesView) {
 }
 
 function* getVariablesView(hud) {
-  function openVariablesView(event, vview) {
+  function openVariablesView(vview) {
     deferred.resolve(vview._variablesView);
   }
 
diff --git a/devtools/client/webconsole/test/browser_console_variables_view_dom_nodes.js b/devtools/client/webconsole/test/browser_console_variables_view_dom_nodes.js
index 6ce5c1db6d6a..2e7827fe0562 100644
--- a/devtools/client/webconsole/test/browser_console_variables_view_dom_nodes.js
+++ b/devtools/client/webconsole/test/browser_console_variables_view_dom_nodes.js
@@ -37,7 +37,7 @@ function test() {
     const jsterm = hud.jsterm;
 
     let deferred = defer();
-    jsterm.once("variablesview-fetched", (_, val) => deferred.resolve(val));
+    jsterm.once("variablesview-fetched", (val) => deferred.resolve(val));
     jsterm.execute("inspect(document.querySelectorAll('div'))");
 
     let variableScope = yield deferred.promise;
diff --git a/devtools/client/webconsole/test/browser_console_variables_view_dont_sort_non_sortable_classes_properties.js b/devtools/client/webconsole/test/browser_console_variables_view_dont_sort_non_sortable_classes_properties.js
index a1e6cb54dc2a..3d98c40124aa 100644
--- a/devtools/client/webconsole/test/browser_console_variables_view_dont_sort_non_sortable_classes_properties.js
+++ b/devtools/client/webconsole/test/browser_console_variables_view_dont_sort_non_sortable_classes_properties.js
@@ -84,7 +84,7 @@ function test() {
   function* testNotSorted(aObject) {
     info("Testing " + aObject);
     let deferred = defer();
-    jsterm.once("variablesview-fetched", (_, aVar) => deferred.resolve(aVar));
+    jsterm.once("variablesview-fetched", (aVar) => deferred.resolve(aVar));
     jsterm.execute("inspect(" + aObject + ")");
 
     let variableScope = yield deferred.promise;
@@ -110,7 +110,7 @@ function test() {
   function* testSorted(aObject) {
     info("Testing " + aObject);
     let deferred = defer();
-    jsterm.once("variablesview-fetched", (_, aVar) => deferred.resolve(aVar));
+    jsterm.once("variablesview-fetched", (aVar) => deferred.resolve(aVar));
     jsterm.execute("inspect(" + aObject + ")");
 
     let variableScope = yield deferred.promise;
diff --git a/devtools/client/webconsole/test/browser_console_variables_view_highlighter.js b/devtools/client/webconsole/test/browser_console_variables_view_highlighter.js
index c1b2194deada..95a7efb295d6 100644
--- a/devtools/client/webconsole/test/browser_console_variables_view_highlighter.js
+++ b/devtools/client/webconsole/test/browser_console_variables_view_highlighter.js
@@ -40,7 +40,7 @@ function onQSAexecuted(msg) {
   );
 }
 
-function onNodeListViewFetched(event, variable) {
+function onNodeListViewFetched(variable) {
   gVariablesView = variable._variablesView;
   ok(gVariablesView, "variables view object");
 
diff --git a/devtools/client/webconsole/test/browser_console_variables_view_while_debugging.js b/devtools/client/webconsole/test/browser_console_variables_view_while_debugging.js
index e83a8d626671..551e1c1e7c72 100644
--- a/devtools/client/webconsole/test/browser_console_variables_view_while_debugging.js
+++ b/devtools/client/webconsole/test/browser_console_variables_view_while_debugging.js
@@ -54,7 +54,7 @@ function* testVariablesView(hud) {
 
   info("Waiting for variable view to appear");
   let variable = yield new Promise(resolve => {
-    jsterm.once("variablesview-fetched", (e, variable) => {
+    jsterm.once("variablesview-fetched", (variable) => {
       resolve(variable);
     });
     executeSoon(() => EventUtils.synthesizeMouse(anchor, 2, 2, {},
diff --git a/devtools/client/webconsole/test/browser_console_variables_view_while_debugging_and_inspecting.js b/devtools/client/webconsole/test/browser_console_variables_view_while_debugging_and_inspecting.js
index 556e7275d7ee..97dc391a2a89 100644
--- a/devtools/client/webconsole/test/browser_console_variables_view_while_debugging_and_inspecting.js
+++ b/devtools/client/webconsole/test/browser_console_variables_view_while_debugging_and_inspecting.js
@@ -57,7 +57,7 @@ function* testVariablesView(hud) {
 
   info("Waiting for variable view to appear");
   let variable = yield new Promise(resolve => {
-    jsterm.once("variablesview-fetched", (e, variable) => {
+    jsterm.once("variablesview-fetched", (variable) => {
       resolve(variable);
     });
     executeSoon(() => EventUtils.synthesizeMouse(anchor, 2, 2, {},
diff --git a/devtools/client/webconsole/test/browser_webconsole_bug_632275_getters_document_width.js b/devtools/client/webconsole/test/browser_webconsole_bug_632275_getters_document_width.js
index 78b288dd8386..eddd5364b45c 100644
--- a/devtools/client/webconsole/test/browser_webconsole_bug_632275_getters_document_width.js
+++ b/devtools/client/webconsole/test/browser_webconsole_bug_632275_getters_document_width.js
@@ -25,7 +25,7 @@ function consoleOpened(hud) {
   hud.jsterm.once("variablesview-fetched", onOpen);
 }
 
-function onViewOpened(hud, event, view) {
+function onViewOpened(hud, view) {
   let doc = gBrowser.contentWindowAsCPOW.wrappedJSObject.document;
 
   findVariableViewProperties(view, [
diff --git a/devtools/client/webconsole/test/browser_webconsole_bug_632347_iterators_generators.js b/devtools/client/webconsole/test/browser_webconsole_bug_632347_iterators_generators.js
index 5a9db1906da0..59059386d69f 100644
--- a/devtools/client/webconsole/test/browser_webconsole_bug_632347_iterators_generators.js
+++ b/devtools/client/webconsole/test/browser_webconsole_bug_632347_iterators_generators.js
@@ -57,7 +57,7 @@ function consoleOpened(HUD) {
   });
 }
 
-function testVariablesView(aWebconsole, aEvent, aView) {
+function testVariablesView(aWebconsole, aView) {
   findVariableViewProperties(aView, [
     { name: "gen1", isGenerator: true },
     { name: "gen2", isGenerator: true },
diff --git a/devtools/client/webconsole/test/browser_webconsole_bug_651501_document_body_autocomplete.js b/devtools/client/webconsole/test/browser_webconsole_bug_651501_document_body_autocomplete.js
index c36b69e4f3a0..3cb631d32d79 100644
--- a/devtools/client/webconsole/test/browser_webconsole_bug_651501_document_body_autocomplete.js
+++ b/devtools/client/webconsole/test/browser_webconsole_bug_651501_document_body_autocomplete.js
@@ -85,7 +85,7 @@ function testPropertyPanel() {
   let jsterm = gHUD.jsterm;
   jsterm.clearOutput();
   jsterm.execute("document", (msg) => {
-    jsterm.once("variablesview-fetched", (evt, view) => {
+    jsterm.once("variablesview-fetched", (view) => {
       deferred.resolve(view);
     });
     let anchor = msg.querySelector(".message-body a");
diff --git a/devtools/client/webconsole/test/browser_webconsole_closure_inspection.js b/devtools/client/webconsole/test/browser_webconsole_closure_inspection.js
index 7dc506554644..4de3682cab28 100644
--- a/devtools/client/webconsole/test/browser_webconsole_closure_inspection.js
+++ b/devtools/client/webconsole/test/browser_webconsole_closure_inspection.js
@@ -81,7 +81,7 @@ function onExecuteGetName(results) {
   });
 }
 
-function onGetNameFetch(evt, view) {
+function onGetNameFetch(view) {
   gVariablesView = view._variablesView;
   ok(gVariablesView, "variables view object");
 
diff --git a/devtools/client/webconsole/test/browser_webconsole_split_escape_key.js b/devtools/client/webconsole/test/browser_webconsole_split_escape_key.js
index 08a14069dd3c..bd258409d337 100644
--- a/devtools/client/webconsole/test/browser_webconsole_split_escape_key.js
+++ b/devtools/client/webconsole/test/browser_webconsole_split_escape_key.js
@@ -116,7 +116,7 @@
    }
 
    function clickMessageAndShowVariablesView() {
-     let result = jsterm.once("variablesview-fetched", (event, vview) => {
+     let result = jsterm.once("variablesview-fetched", (vview) => {
        variablesView = vview;
      });
 
diff --git a/devtools/client/webconsole/test/head.js b/devtools/client/webconsole/test/head.js
index 1321b93e123c..28401f4b9d13 100644
--- a/devtools/client/webconsole/test/head.js
+++ b/devtools/client/webconsole/test/head.js
@@ -1249,7 +1249,7 @@ function waitForMessages(options) {
     return rule.matched.size == count;
   }
 
-  function onMessagesAdded(event, newMessages) {
+  function onMessagesAdded(newMessages) {
     for (let msg of newMessages) {
       let elem = msg.node;
       let location = getRenderedSource(elem);
@@ -1332,7 +1332,7 @@ function waitForMessages(options) {
       });
     }
 
-    onMessagesAdded("new-messages", messages);
+    onMessagesAdded(messages);
 
     if (!allRulesMatched()) {
       listenerAdded = true;
@@ -1529,7 +1529,7 @@ function checkOutputForInputs(hud, inputTests) {
     yield promise.resolve(null);
   }
 
-  function onVariablesViewOpen(entry, {resolve, reject}, event, view, options) {
+  function onVariablesViewOpen(entry, {resolve, reject}, {view, options}) {
     info("Variables view opened");
     let label = entry.variablesViewLabel || entry.output;
     if (typeof label == "string" && options.label != label) {
diff --git a/devtools/client/webconsole/webconsole.js b/devtools/client/webconsole/webconsole.js
index d9f2522feb49..97ddd139df54 100644
--- a/devtools/client/webconsole/webconsole.js
+++ b/devtools/client/webconsole/webconsole.js
@@ -25,7 +25,7 @@ const {PrefObserver} = require("devtools/client/shared/prefs");
 loader.lazyServiceGetter(this, "clipboardHelper",
                          "@mozilla.org/widget/clipboardhelper;1",
                          "nsIClipboardHelper");
-loader.lazyRequireGetter(this, "EventEmitter", "devtools/shared/old-event-emitter");
+loader.lazyRequireGetter(this, "EventEmitter", "devtools/shared/event-emitter");
 loader.lazyRequireGetter(this, "ConsoleOutput", "devtools/client/webconsole/console-output", true);
 loader.lazyRequireGetter(this, "Messages", "devtools/client/webconsole/console-output", true);
 loader.lazyRequireGetter(this, "EnvironmentClient", "devtools/shared/client/environment-client");
diff --git a/devtools/client/webconsole/webpack.config.js b/devtools/client/webconsole/webpack.config.js
index 956ed399a5db..f9706d984a0d 100644
--- a/devtools/client/webconsole/webpack.config.js
+++ b/devtools/client/webconsole/webpack.config.js
@@ -97,6 +97,7 @@ webpackConfig.resolve = {
 
     "devtools/shared/fronts/timeline": path.join(__dirname, "../../client/shared/webpack/shims/fronts-timeline-shim"),
     "devtools/shared/old-event-emitter": "devtools-modules/src/utils/event-emitter",
+    "devtools/shared/event-emitter": "devtools-modules/src/utils/event-emitter",
     "devtools/shared/client/debugger-client": path.join(__dirname, "new-console-output/test/fixtures/DebuggerClient"),
     "devtools/shared/platform/clipboard": path.join(__dirname, "../../client/shared/webpack/shims/platform-clipboard-stub"),
     "devtools/shared/platform/stack": path.join(__dirname, "../../client/shared/webpack/shims/platform-stack-stub"),
diff --git a/dom/security/test/cors/browser_CORS-console-warnings.js b/dom/security/test/cors/browser_CORS-console-warnings.js
index b4b90e3f058c..ec844d5d30da 100644
--- a/dom/security/test/cors/browser_CORS-console-warnings.js
+++ b/dom/security/test/cors/browser_CORS-console-warnings.js
@@ -16,7 +16,7 @@ var webconsole = null;
 var messages_seen = 0;
 var expected_messages = 50;
 
-function on_new_message(event, new_messages) {
+function on_new_message(new_messages) {
   for (let message of new_messages) {
     let elem = message.node;
     let text = elem.textContent;
diff --git a/testing/talos/talos/tests/devtools/addon/content/damp.js b/testing/talos/talos/tests/devtools/addon/content/damp.js
index 4e8600225237..7d0beef1b67b 100644
--- a/testing/talos/talos/tests/devtools/addon/content/damp.js
+++ b/testing/talos/talos/tests/devtools/addon/content/damp.js
@@ -352,7 +352,7 @@ Damp.prototype = {
 
     // Resolve once the last message has been received.
     let allMessagesReceived = new Promise(resolve => {
-      function receiveMessages(e, messages) {
+      function receiveMessages(messages) {
         for (let m of messages) {
           if (m.node.textContent.includes("damp " + TOTAL_MESSAGES)) {
             webconsole.hud.ui.off("new-messages", receiveMessages);
@@ -444,7 +444,7 @@ Damp.prototype = {
 
     // Resolve once the first message is received.
     let onMessageReceived = new Promise(resolve => {
-      function receiveMessages(e, messages) {
+      function receiveMessages(messages) {
         for (let m of messages) {
           resolve(m);
         }