--- a/services/.eslintrc.js
+++ b/services/.eslintrc.js
@@ -16,11 +16,10 @@ module.exports = {
     "no-ex-assign": "warn",
     "no-func-assign": "warn",
     "no-native-reassign": "warn",
     "no-nested-ternary": "warn",
     "no-octal": "warn",
     "no-redeclare": "warn",
     "no-unreachable": "warn",
     "no-unsafe-finally": "warn",
-    "no-useless-call": "warn"
   }
 };

--- a/services/cloudsync/CloudSyncEventSource.jsm
+++ b/services/cloudsync/CloudSyncEventSource.jsm
@@ -49,17 +49,17 @@ EventSource.prototype = {
 
   emit(type, arg) {
     if (!this.listeners.has(type)) {
       return;
     }
     CommonUtils.nextTick(
       function() {
         for (let listener of this.listeners.get(type)) {
-          listener.call(undefined, arg);
+          listener(arg);
         }
       },
       this
     );
   },
 };
 
 this.EventSource = EventSource;

--- a/services/fxaccounts/tests/browser/browser_device_connected.js
+++ b/services/fxaccounts/tests/browser/browser_device_connected.js
@@ -7,17 +7,17 @@ const { MockRegistrar } =
   Cu.import("resource://testing-common/MockRegistrar.jsm", {});
 
 const StubAlertsService = {
   QueryInterface: XPCOMUtils.generateQI([Ci.nsIAlertsService, Ci.nsISupports]),
 
   showAlertNotification(image, title, text, clickable, cookie, clickCallback) {
     // We can't simulate a click on the alert popup,
     // so instead we call the click listener ourselves directly
-    clickCallback.observe.call(clickCallback, null, "alertclickcallback", null);
+    clickCallback.observe(null, "alertclickcallback", null);
   }
 }
 
 add_task(function*() {
   gBrowser.selectedBrowser.loadURI("about:robots");
   yield waitForDocLoadComplete();
 
   MockRegistrar.register("@mozilla.org/alerts-service;1", StubAlertsService);

--- a/services/sync/modules/addonsreconciler.js
+++ b/services/sync/modules/addonsreconciler.js
@@ -482,17 +482,17 @@ AddonsReconciler.prototype = {
    *        The new state of the add-on. From this.addons.
    */
   _addChange: function _addChange(date, change, state) {
     this._log.info("Change recorded for " + state.id);
     this._changes.push([date, change, state.id]);
 
     for (let listener of this._listeners) {
       try {
-        listener.changeListener.call(listener, date, change, state);
+        listener.changeListener(date, change, state);
       } catch (ex) {
         this._log.warn("Exception calling change listener", ex);
       }
     }
   },
 
   /**
    * Obtain the set of changes to add-ons since the date passed.

--- a/services/sync/tests/unit/test_clients_engine.js
+++ b/services/sync/tests/unit/test_clients_engine.js
@@ -1077,17 +1077,17 @@ add_task(async function test_upload_afte
     _("First sync. 2 records downloaded.");
     strictEqual(engine.lastRecordUpload, 0);
     engine._sync();
 
     _("Send tab to client");
     engine.sendCommand("displayURI", ["https://example.com", engine.localID, "Yak Herders Anonymous"], deviceBID);
 
     const oldUploadOutgoing = SyncEngine.prototype._uploadOutgoing;
-    SyncEngine.prototype._uploadOutgoing = () => engine._onRecordsWritten.call(engine, [], [deviceBID]);
+    SyncEngine.prototype._uploadOutgoing = () => engine._onRecordsWritten([], [deviceBID]);
     engine._sync();
 
     let collection = server.getCollection("foo", "clients");
     let deviceBPayload = JSON.parse(JSON.parse(collection.payload(deviceBID)).ciphertext);
     compareCommands(deviceBPayload.commands, [{
       command: "displayURI", args: ["https://deviceclink.com", deviceCID, "Device C link"]
     }], "Should be the same because the upload failed");
 
@@ -1177,17 +1177,17 @@ add_task(async function test_keep_cleare
   }), now - 10));
 
   try {
     _("First sync. Download remote and our record.");
     strictEqual(engine.lastRecordUpload, 0);
 
     let collection = server.getCollection("foo", "clients");
     const oldUploadOutgoing = SyncEngine.prototype._uploadOutgoing;
-    SyncEngine.prototype._uploadOutgoing = () => engine._onRecordsWritten.call(engine, [], [deviceBID]);
+    SyncEngine.prototype._uploadOutgoing = () => engine._onRecordsWritten([], [deviceBID]);
     let commandsProcessed = 0;
     engine._handleDisplayURIs = (uris) => { commandsProcessed = uris.length };
 
     engine._sync();
     engine.processIncomingCommands(); // Not called by the engine.sync(), gotta call it ourselves
     equal(commandsProcessed, 2, "We processed 2 commands");
 
     let localRemoteRecord = JSON.parse(JSON.parse(collection.payload(engine.localID)).ciphertext);