diff --git a/CHANGELOG.md b/CHANGELOG.md
index 08dfef29..a40e5ff2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -110,6 +110,7 @@ Please also have a look at our
 
 ### Fixed
 
+- Parse selector functions (like `:not`) with comma-separated arguments (#1292)
 - Parse quoted attribute selector value containing comma (#1323)
 - Allow comma in selectors (e.g. `:not(html, body)`) (#1293)
 - Insert `Rule` before sibling even with different property name
diff --git a/src/RuleSet/DeclarationBlock.php b/src/RuleSet/DeclarationBlock.php
index d0b9654c..68926deb 100644
--- a/src/RuleSet/DeclarationBlock.php
+++ b/src/RuleSet/DeclarationBlock.php
@@ -43,8 +43,9 @@ public static function parse(ParserState $parserState, ?CSSList $list = null): ?
             $selectors = [];
             $selectorParts = [];
             $stringWrapperCharacter = null;
+            $functionNestingLevel = 0;
             $consumedNextCharacter = false;
-            static $stopCharacters = ['{', '}', '\'', '"', ','];
+            static $stopCharacters = ['{', '}', '\'', '"', '(', ')', ','];
             do {
                 if (!$consumedNextCharacter) {
                     $selectorParts[] = $parserState->consume(1);
@@ -64,8 +65,21 @@ public static function parse(ParserState $parserState, ?CSSList $list = null): ?
                             }
                         }
                         break;
-                    case ',':
+                    case '(':
                         if (!\is_string($stringWrapperCharacter)) {
+                            ++$functionNestingLevel;
+                        }
+                        break;
+                    case ')':
+                        if (!\is_string($stringWrapperCharacter)) {
+                            if ($functionNestingLevel <= 0) {
+                                throw new UnexpectedTokenException('anything but', ')');
+                            }
+                            --$functionNestingLevel;
+                        }
+                        break;
+                    case ',':
+                        if (!\is_string($stringWrapperCharacter) && $functionNestingLevel === 0) {
                             $selectors[] = \implode('', $selectorParts);
                             $selectorParts = [];
                             $parserState->consume(1);
@@ -74,6 +88,9 @@ public static function parse(ParserState $parserState, ?CSSList $list = null): ?
                         break;
                 }
             } while (!\in_array($nextCharacter, ['{', '}'], true) || \is_string($stringWrapperCharacter));
+            if ($functionNestingLevel !== 0) {
+                throw new UnexpectedTokenException(')', $nextCharacter);
+            }
             $selectors[] = \implode('', $selectorParts); // add final or only selector
             $result->setSelectors($selectors, $list);
             if ($parserState->comes('{')) {
diff --git a/tests/Unit/RuleSet/DeclarationBlockTest.php b/tests/Unit/RuleSet/DeclarationBlockTest.php
index 468a8515..4419ba0f 100644
--- a/tests/Unit/RuleSet/DeclarationBlockTest.php
+++ b/tests/Unit/RuleSet/DeclarationBlockTest.php
@@ -67,6 +67,7 @@ public static function provideSelector(): array
             'pseudo-class' => [':hover'],
             'type & pseudo-class' => ['a:hover'],
             '`not`' => [':not(#your-mug)'],
+            '`not` with multiple arguments' => [':not(#your-mug, .their-mug)'],
             'pseudo-element' => ['::before'],
             'attribute with `"`' => ['[alt="{}()[]\\"\',"]'],
             'attribute with `\'`' => ['[alt=\'{}()[]"\\\',\']'],
@@ -114,6 +115,40 @@ public function parsesTwoCommaSeparatedSelectors(string $firstSelector, string $
         self::assertSame([$firstSelector, $secondSelector], self::getSelectorsAsStrings($subject));
     }
 
+    /**
+     * @return array<non-empty-string, array{0: non-empty-string}>
+     */
+    public static function provideInvalidSelector(): array
+    {
+        // TODO: the `parse` method consumes the first character without inspection,
+        // so the 'lone' test strings are prefixed with a space.
+        return [
+            'lone `(`' => [' ('],
+            'lone `)`' => [' )'],
+            'unclosed `(`' => [':not(#your-mug'],
+            'extra `)`' => [':not(#your-mug))'],
+        ];
+    }
+
+    /**
+     * @test
+     *
+     * @param non-empty-string $selector
+     *
+     * @dataProvider provideInvalidSelector
+     */
+    public function parseSkipsBlockWithInvalidSelector(string $selector): void
+    {
+        static $nextCss = ' .next {}';
+        $css = $selector . ' {}' . $nextCss;
+        $parserState = new ParserState($css, Settings::create());
+
+        $subject = DeclarationBlock::parse($parserState);
+
+        self::assertNull($subject);
+        self::assertTrue($parserState->comes($nextCss));
+    }
+
     /**
      * @return array<string>
      */