diff --git a/.eslintrc.json b/.eslintrc.json
index efe793be93..e640ab56e8 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -26,6 +26,7 @@
         "no-trailing-spaces": "error",
         "no-underscore-dangle": "warn",
         "no-unneeded-ternary": "error",
+        "no-unsafe-negation": "error",
         "no-useless-escape": "error",
         "object-curly-spacing": ["error", "always"],
         "one-var": ["error", "never"],
diff --git a/js/functions.js b/js/functions.js
index a0f339a7f3..491c5968fe 100644
--- a/js/functions.js
+++ b/js/functions.js
@@ -3980,7 +3980,7 @@ Functions.showIndexEditDialog = function ($outer) {
  *                    in the whole body
  **/
 Functions.showHints = function ($div) {
-    if ($div === undefined || ! $div instanceof jQuery || $div.length === 0) {
+    if ($div === undefined || !($div instanceof jQuery) || $div.length === 0) {
         $div = $('body');
     }
     $div.find('.pma_hint').each(function () {
@@ -4332,7 +4332,7 @@ Functions.slidingMessage = function (msg, $obj) {
         // Don't show an empty message
         return false;
     }
-    if ($obj === undefined || ! $obj instanceof jQuery || $obj.length === 0) {
+    if ($obj === undefined || !($obj instanceof jQuery) || $obj.length === 0) {
         // If the second argument was not supplied,
         // we might have to create a new DOM node.
         if ($('#PMA_slidingMessage').length === 0) {