diff --git a/CHANGELOG.md b/CHANGELOG.md
index fc07eba..2e50ee7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,12 @@
 # Changelog
 
+## 1.2.7 - 2026-04-22
+
+### Fixed
+- **Polyfill stub classes incorrectly prefixed**: Symfony polyfill packages (`polyfill-intl-normalizer`, `polyfill-php73`, `polyfill-php80`) ship stub files that declare classes in the global namespace so they act as fallbacks when the corresponding PHP extension or version is missing. `ClassmapReplacer` prefixed these stubs alongside other global classes, which broke the fallbacks and caused fatal `Class "X" not found` errors at runtime on servers that lacked the native implementation — most visibly `Normalizer` on hosts without the `intl` extension, but also `Attribute`, `JsonException`, `PhpToken`, and `UnhandledMatchError` on older PHP versions. The built-in allowlist now covers these five classes, plus the related `CompileError`, `UnitEnum`, `BackedEnum`, `SensitiveParameter`, and `Override` globals.
+
+---
+
 ## 1.2.6 - 2026-04-18
 
 ### Fixed
diff --git a/composer.json b/composer.json
index 6b96630..09e67e3 100644
--- a/composer.json
+++ b/composer.json
@@ -2,7 +2,7 @@
     "name": "veronalabs/wp-scoper",
     "description": "A Composer plugin that prefixes namespaces in WordPress plugin dependencies to prevent conflicts",
     "type": "composer-plugin",
-    "version": "1.2.6",
+    "version": "1.2.7",
     "license": "MIT",
     "authors": [
         {
diff --git a/src/Replacer/ClassmapReplacer.php b/src/Replacer/ClassmapReplacer.php
index b7a7936..6b01cfd 100644
--- a/src/Replacer/ClassmapReplacer.php
+++ b/src/Replacer/ClassmapReplacer.php
@@ -15,15 +15,20 @@ class ClassmapReplacer implements ReplacerInterface
     /** @var array<string> PHP built-in classes to never prefix */
     private static $phpBuiltinClasses = [
         'stdClass', 'Exception', 'ErrorException', 'Error', 'TypeError', 'ValueError',
-        'ArithmeticError', 'DivisionByZeroError', 'ParseError', 'Throwable',
+        'ArithmeticError', 'DivisionByZeroError', 'ParseError', 'CompileError',
+        'Throwable', 'UnhandledMatchError',
         'RuntimeException', 'LogicException', 'InvalidArgumentException',
         'BadMethodCallException', 'BadFunctionCallException', 'DomainException',
         'LengthException', 'OutOfBoundsException', 'OutOfRangeException',
         'OverflowException', 'RangeException', 'UnderflowException',
         'UnexpectedValueException',
         'Iterator', 'IteratorAggregate', 'ArrayAccess', 'Serializable',
-        'Countable', 'Traversable', 'JsonSerializable', 'Stringable',
+        'Countable', 'Traversable', 'JsonSerializable', 'JsonException', 'Stringable',
+        'UnitEnum', 'BackedEnum',
         'Generator', 'Closure', 'Fiber',
+        'Attribute', 'SensitiveParameter', 'Override',
+        'PhpToken',
+        'Normalizer',
         'DateTime', 'DateTimeImmutable', 'DateTimeInterface', 'DateTimeZone',
         'DateInterval', 'DatePeriod',
         'SplFileInfo', 'SplFileObject', 'SplTempFileObject',
diff --git a/tests/Unit/Replacer/ClassmapReplacerTest.php b/tests/Unit/Replacer/ClassmapReplacerTest.php
index a4ef4d0..098aa42 100644
--- a/tests/Unit/Replacer/ClassmapReplacerTest.php
+++ b/tests/Unit/Replacer/ClassmapReplacerTest.php
@@ -91,6 +91,43 @@ public function testDoesNotPrefixPhpBuiltins(): void
         $this->assertStringNotContainsString('WPS_stdClass', $result);
     }
 
+    /**
+     * @dataProvider polyfillStubClassProvider
+     */
+    public function testDoesNotPrefixPolyfillStubClasses(string $className): void
+    {
+        // Symfony polyfill-* packages ship stubs that declare these classes in
+        // the global namespace so they act as a fallback when the corresponding
+        // PHP extension/version is missing. Prefixing the stub class breaks the
+        // fallback and causes "Class X not found" fatals on servers that lack
+        // the native implementation (e.g. PHP without the intl extension).
+        $replacer = new ClassmapReplacer('WPS_', [$className]);
+        $stub = "<?php\nclass {$className} {}\n";
+        $usage = "<?php\n\$x = new {$className}();\n{$className}::FOO;";
+
+        $this->assertStringNotContainsString(
+            'WPS_' . $className,
+            $replacer->replace($stub),
+            "Polyfill stub declaration for {$className} must stay in the global namespace"
+        );
+        $this->assertStringNotContainsString(
+            'WPS_' . $className,
+            $replacer->replace($usage),
+            "References to global polyfilled {$className} must not be prefixed"
+        );
+    }
+
+    public function polyfillStubClassProvider(): array
+    {
+        return [
+            'Attribute (PHP 8.0)'              => ['Attribute'],
+            'JsonException (PHP 7.3)'          => ['JsonException'],
+            'Normalizer (intl extension)'      => ['Normalizer'],
+            'PhpToken (PHP 8.0)'               => ['PhpToken'],
+            'UnhandledMatchError (PHP 8.0)'    => ['UnhandledMatchError'],
+        ];
+    }
+
     public function testDoesNotDoublePrefixClass(): void
     {
         $replacer = new ClassmapReplacer('WPS_', ['MyGlobalClass']);