6 files changed, 5 insertions, 14 deletions
diff --git a/toolkit/.eslintrc.js b/toolkit/.eslintrc.js
index 181f19f29f..891a114b35 100644
--- a/toolkit/.eslintrc.js
+++ b/toolkit/.eslintrc.js
@@ -111,9 +111,6 @@ module.exports = {
     // No reassigning native JS objects
     "no-native-reassign": "error",
 
-    // No (!foo in bar)
-    "no-negated-in-lhs": "error",
-
     // Nested ternary statements are confusing
     "no-nested-ternary": "error",
 
diff --git a/toolkit/components/osfile/modules/osfile_unix_front.jsm b/toolkit/components/osfile/modules/osfile_unix_front.jsm
index 19a27ae1aa..bd60d4d841 100644
--- a/toolkit/components/osfile/modules/osfile_unix_front.jsm
+++ b/toolkit/components/osfile/modules/osfile_unix_front.jsm
@@ -838,7 +838,7 @@
       * implementation.
       */
      File.DirectoryIterator.Entry.toMsg = function toMsg(value) {
-       if (!value instanceof File.DirectoryIterator.Entry) {
+       if (!(value instanceof File.DirectoryIterator.Entry)) {
          throw new TypeError("parameter of " +
            "File.DirectoryIterator.Entry.toMsg must be a " +
            "File.DirectoryIterator.Entry");
@@ -905,7 +905,7 @@
       * is asymmetric and returns an object with a different implementation.
       */
      File.Info.toMsg = function toMsg(stat) {
-       if (!stat instanceof File.Info) {
+       if (!(stat instanceof File.Info)) {
          throw new TypeError("parameter of File.Info.toMsg must be a File.Info");
        }
        let serialized = {};
diff --git a/toolkit/components/osfile/modules/osfile_win_front.jsm b/toolkit/components/osfile/modules/osfile_win_front.jsm
index 387dd08b56..1123b251ca 100644
--- a/toolkit/components/osfile/modules/osfile_win_front.jsm
+++ b/toolkit/components/osfile/modules/osfile_win_front.jsm
@@ -909,7 +909,7 @@
       * implementation.
       */
      File.DirectoryIterator.Entry.toMsg = function toMsg(value) {
-       if (!value instanceof File.DirectoryIterator.Entry) {
+       if (!(value instanceof File.DirectoryIterator.Entry)) {
          throw new TypeError("parameter of " +
            "File.DirectoryIterator.Entry.toMsg must be a " +
            "File.DirectoryIterator.Entry");
@@ -958,7 +958,7 @@
       * is asymmetric and returns an object with a different implementation.
       */
      File.Info.toMsg = function toMsg(stat) {
-       if (!stat instanceof File.Info) {
+       if (!(stat instanceof File.Info)) {
          throw new TypeError("parameter of File.Info.toMsg must be a File.Info");
        }
        let serialized = {};
diff --git a/toolkit/components/reader/.eslintrc.js b/toolkit/components/reader/.eslintrc.js
index 1c09e0bf79..617c1f9cfa 100644
--- a/toolkit/components/reader/.eslintrc.js
+++ b/toolkit/components/reader/.eslintrc.js
@@ -109,9 +109,6 @@ module.exports = {
     // No reassigning native JS objects
     "no-native-reassign": "error",
 
-    // No (!foo in bar)
-    "no-negated-in-lhs": "error",
-
     // Nested ternary statements are confusing
     "no-nested-ternary": "error",
 
diff --git a/toolkit/components/webextensions/.eslintrc.js b/toolkit/components/webextensions/.eslintrc.js
index 70196fc6ac..70f91ab6d2 100644
--- a/toolkit/components/webextensions/.eslintrc.js
+++ b/toolkit/components/webextensions/.eslintrc.js
@@ -173,9 +173,6 @@ module.exports = { // eslint-disable-line no-undef
     // No reassigning native JS objects
     "no-native-reassign": "error",
 
-    // No (!foo in bar)
-    "no-negated-in-lhs": "error",
-
     // Nested ternary statements are confusing
     "no-nested-ternary": "error",
 
diff --git a/toolkit/modules/Sqlite.jsm b/toolkit/modules/Sqlite.jsm
index e8d986c0e5..6f7a7d94c1 100644
--- a/toolkit/modules/Sqlite.jsm
+++ b/toolkit/modules/Sqlite.jsm
@@ -995,7 +995,7 @@ function cloneStorageConnection(options) {
   if (!source) {
     throw new TypeError("connection not specified in clone options.");
   }
-  if (!source instanceof Ci.mozIStorageAsyncConnection) {
+  if (!(source instanceof Ci.mozIStorageAsyncConnection)) {
     throw new TypeError("Connection must be a valid Storage connection.");
   }