diff --git a/composer.json b/composer.json
index 78a65ec..e9959a9 100644
--- a/composer.json
+++ b/composer.json
@@ -19,10 +19,10 @@
     ],
     "require": {
         "php": "^7.2",
-        "symfony/polyfill-ctype": "^1.8.0"
+        "symfony/polyfill-mbstring": "^1.8.0"
     },
     "require-dev": {
-        "narrowspark/php-cs-fixer-config": "^2.1.0",
+        "narrowspark/php-cs-fixer-config": "^3.0.1",
         "phpstan/phpstan": "^0.9.0",
         "phpstan/phpstan-phpunit": "^0.9.0",
         "phpunit/phpunit": "^7.0.0",
diff --git a/src/Traits/PrettyArrayPrintTrait.php b/src/Traits/PrettyArrayPrintTrait.php
index 01eddd3..ecf8978 100644
--- a/src/Traits/PrettyArrayPrintTrait.php
+++ b/src/Traits/PrettyArrayPrintTrait.php
@@ -19,8 +19,8 @@ protected static function getPrettyPrintArray(array $data, int $indentLevel = 1)
 
         foreach ($data as $key => $value) {
             if (! \is_int($key)) {
-                if (\is_string($key) && (\class_exists($key) || \interface_exists($key)) && \ctype_upper($key[0])) {
-                    $key = \sprintf('\\%s::class', \ltrim($key, '\\'));
+                if (self::isClass($key)) {
+                    $key = self::dumpLiteralClass($key);
                 } else {
                     $key = \sprintf("'%s'", $key);
                 }
@@ -53,8 +53,8 @@ protected static function createValue($value, int $indentLevel): string
             return self::getPrettyPrintArray($value, $indentLevel + 1);
         }
 
-        if (\is_string($value) && (\class_exists($value) || \interface_exists($value)) && \ctype_upper($value[0])) {
-            return \sprintf('\\%s::class', \ltrim($value, '\\'));
+        if (self::isClass($value)) {
+            return self::dumpLiteralClass($value);
         }
 
         if (\is_numeric($value)) {
@@ -67,4 +67,38 @@ protected static function createValue($value, int $indentLevel): string
 
         return \var_export($value, true);
     }
+
+    /**
+     * Dumps a string to a literal (aka PHP Code) class value.
+     *
+     * @param string $class
+     *
+     * @return string
+     */
+    private static function dumpLiteralClass(string $class): string
+    {
+        $class = \str_replace('\\\\', '\\', $class);
+        $class = \sprintf('%s::class', $class);
+
+        return \mb_strpos($class, '\\') === 0 ? $class : '\\' . $class;
+    }
+
+    /**
+     * Check if entry is a class.
+     *
+     * @param mixed $key
+     *
+     * @return bool
+     */
+    private static function isClass($key): bool
+    {
+        if (! \is_string($key)) {
+            return false;
+        }
+
+        $key       = \ltrim($key, '\\');
+        $firstChar = \mb_substr($key, 0, 1);
+
+        return (\class_exists($key) || \interface_exists($key)) && \mb_strtolower($firstChar) !== $firstChar;
+    }
 }
diff --git a/tests/PrettyArrayTest.php b/tests/PrettyArrayTest.php
index 39f622e..dbae3e3 100644
--- a/tests/PrettyArrayTest.php
+++ b/tests/PrettyArrayTest.php
@@ -7,19 +7,23 @@
 use PHPUnit\Framework\TestCase;
 use Throwable;
 
-class PrettyArrayTest extends TestCase
+/**
+ * @internal
+ */
+final class PrettyArrayTest extends TestCase
 {
     public function arrayOutProvider(): array
     {
         return [
             [[], '[' . \PHP_EOL . \PHP_EOL . ']'],
-            [[1], '[' . PHP_EOL . '    0 => 1,' . PHP_EOL . ']'],
-            [[1, 2, 3], '[' . PHP_EOL . '    0 => 1,' . PHP_EOL . '    1 => 2,' . PHP_EOL . '    2 => 3,' . PHP_EOL . ']'],
-            [[1, '2', 3], '[' . PHP_EOL . '    0 => 1,' . PHP_EOL . '    1 => \'2\',' . PHP_EOL . '    2 => 3,' . PHP_EOL . ']'],
-            [['foo' => 1, [2, 3]], '[' . PHP_EOL . '    \'foo\' => 1,' . PHP_EOL . '    0 => [' . PHP_EOL . '        0 => 2,' . PHP_EOL . '        1 => 3,' . PHP_EOL . '    ],' . PHP_EOL . ']'],
-            [[1 => ['foo'], 'bar' => 2], '[' . PHP_EOL . '    1 => [' . PHP_EOL . '        0 => \'foo\',' . PHP_EOL . '    ],' . PHP_EOL . '    \'bar\' => 2,' . PHP_EOL . ']'],
-            [[1 => Exception::class, Throwable::class => 'error', 'foo' => 'bar', 'fooa' => 1.2], '[' . PHP_EOL . '    1 => \\Exception::class,' . PHP_EOL . '    \\Throwable::class => \'error\',' . PHP_EOL . '    \'foo\' => \'bar\',' . PHP_EOL . '    \'fooa\' => 1.2,' . PHP_EOL . ']'],
-            [[1 => 'foo', '188.29614911019327165' => 'bar', 'foo' => '889614911019327165', 'fooa' => 18896141256], '[' . PHP_EOL . '    1 => \'foo\',' . PHP_EOL . '    \'188.29614911019327165\' => \'bar\',' . PHP_EOL . '    \'foo\' => \'889614911019327165\',' . PHP_EOL . '    \'fooa\' => 18896141256,' . PHP_EOL . ']'],
+            [[1], '[' . \PHP_EOL . '    0 => 1,' . \PHP_EOL . ']'],
+            [[1, 2, 3], '[' . \PHP_EOL . '    0 => 1,' . \PHP_EOL . '    1 => 2,' . \PHP_EOL . '    2 => 3,' . \PHP_EOL . ']'],
+            [[1, '2', 3], '[' . \PHP_EOL . '    0 => 1,' . \PHP_EOL . '    1 => \'2\',' . \PHP_EOL . '    2 => 3,' . \PHP_EOL . ']'],
+            [['foo' => 1, [2, 3]], '[' . \PHP_EOL . '    \'foo\' => 1,' . \PHP_EOL . '    0 => [' . \PHP_EOL . '        0 => 2,' . \PHP_EOL . '        1 => 3,' . \PHP_EOL . '    ],' . \PHP_EOL . ']'],
+            [[1 => ['foo'], 'bar' => 2], '[' . \PHP_EOL . '    1 => [' . \PHP_EOL . '        0 => \'foo\',' . \PHP_EOL . '    ],' . \PHP_EOL . '    \'bar\' => 2,' . \PHP_EOL . ']'],
+            [['\\Exception', '\\\\' . Exception::class], '[' . \PHP_EOL . '    0 => \\Exception::class,' . \PHP_EOL . '    1 => \\Exception::class,' . \PHP_EOL . ']'],
+            [[1 => Exception::class, Throwable::class => 'error', 'foo' => 'bar', 'fooa' => 1.2], '[' . \PHP_EOL . '    1 => \\Exception::class,' . \PHP_EOL . '    \\Throwable::class => \'error\',' . \PHP_EOL . '    \'foo\' => \'bar\',' . \PHP_EOL . '    \'fooa\' => 1.2,' . \PHP_EOL . ']'],
+            [[1 => 'foo', '188.29614911019327165' => 'bar', 'foo' => '889614911019327165', 'fooa' => 18896141256], '[' . \PHP_EOL . '    1 => \'foo\',' . \PHP_EOL . '    \'188.29614911019327165\' => \'bar\',' . \PHP_EOL . '    \'foo\' => \'889614911019327165\',' . \PHP_EOL . '    \'fooa\' => 18896141256,' . \PHP_EOL . ']'],
         ];
     }
 
@@ -31,6 +35,6 @@ public function arrayOutProvider(): array
      */
     public function testConvertsValueToValidPhp($array, $expected): void
     {
-        self::assertEquals($expected, PrettyArray::print($array));
+        $this->assertEquals($expected, PrettyArray::print($array));
     }
 }