diff --git a/src/js/contentscript.js b/src/js/contentscript.js
index eb97b75fa..7d628f2ba 100644
--- a/src/js/contentscript.js
+++ b/src/js/contentscript.js
@@ -480,6 +480,7 @@ vAPI.DOMFilterer = (function() {
                 [ ':matches-css', PSelectorMatchesCSSTask ],
                 [ ':matches-css-after', PSelectorMatchesCSSAfterTask ],
                 [ ':matches-css-before', PSelectorMatchesCSSBeforeTask ],
+                [ ':not', PSelectorIfNotTask ],
                 [ ':xpath', PSelectorXpathTask ]
             ]);
         }
diff --git a/src/js/static-ext-filtering.js b/src/js/static-ext-filtering.js
index 5a5f8e7b7..f46daf073 100644
--- a/src/js/static-ext-filtering.js
+++ b/src/js/static-ext-filtering.js
@@ -159,6 +159,7 @@
                 'matches-css',
                 'matches-css-after',
                 'matches-css-before',
+                'not',
                 'xpath'
                 ].join('|'),
             ')\\('
@@ -209,6 +210,9 @@
         };
 
         var compileConditionalSelector = function(s) {
+            if ( isValidCSSSelector(s) ) {
+                return { selector: s, tasks: [] };
+            }
             // https://github.com/AdguardTeam/ExtendedCss/issues/31#issuecomment-302391277
             // Prepend `:scope ` if needed.
             if ( reNeedScope.test(s) ) {
@@ -241,6 +245,7 @@
             [ ':matches-css', compileCSSDeclaration ],
             [ ':matches-css-after', compileCSSDeclaration ],
             [ ':matches-css-before', compileCSSDeclaration ],
+            [ ':not', compileConditionalSelector ],
             [ ':xpath', compileXpathExpression ]
         ]);
 
@@ -293,7 +298,8 @@
                     raw.push(':has', '(', decompile(task[1]), ')');
                     break;
                 case ':if-not':
-                    raw.push(task[0], '(', decompile(task[1]), ')');
+                case ':not':
+                    raw.push(':not', '(', decompile(task[1]), ')');
                     break;
                 }
             }