diff --git a/src/Symfony/Component/DependencyInjection/ParameterBag/EnvPlaceholderParameterBag.php b/src/Symfony/Component/DependencyInjection/ParameterBag/EnvPlaceholderParameterBag.php
index f8af61e6b94c4..14277f86c2512 100644
--- a/src/Symfony/Component/DependencyInjection/ParameterBag/EnvPlaceholderParameterBag.php
+++ b/src/Symfony/Component/DependencyInjection/ParameterBag/EnvPlaceholderParameterBag.php
@@ -49,7 +49,7 @@ public function get(string $name): array|bool|string|int|float|\UnitEnum|null
             }
 
             $uniqueName = md5($name.'_'.self::$counter++);
-            $placeholder = sprintf('%s_%s_%s', $this->getEnvPlaceholderUniquePrefix(), strtr($env, ':-.', '___'), $uniqueName);
+            $placeholder = sprintf('%s_%s_%s', $this->getEnvPlaceholderUniquePrefix(), strtr($env, ':-.\\', '____'), $uniqueName);
             $this->envPlaceholders[$env][$placeholder] = $placeholder;
 
             return $placeholder;
diff --git a/src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php b/src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php
index c9a41d3db9b5a..bbf618b981e85 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php
@@ -51,6 +51,7 @@
 use Symfony\Component\DependencyInjection\Tests\Fixtures\FooWithAbstractArgument;
 use Symfony\Component\DependencyInjection\Tests\Fixtures\ScalarFactory;
 use Symfony\Component\DependencyInjection\Tests\Fixtures\SimilarArgumentsDummy;
+use Symfony\Component\DependencyInjection\Tests\Fixtures\StringBackedEnum;
 use Symfony\Component\DependencyInjection\Tests\Fixtures\WitherStaticReturnType;
 use Symfony\Component\DependencyInjection\TypedReference;
 use Symfony\Component\ExpressionLanguage\Expression;
@@ -545,6 +546,23 @@ public function testEnvExpressionFunction()
         $this->assertEquals('Foo value', $container->get('bar')->foo);
     }
 
+    public function testGetEnvCountersWithEnum()
+    {
+        $bag = new EnvPlaceholderParameterBag();
+        $config = new ContainerBuilder($bag);
+        $config->resolveEnvPlaceholders([
+            $bag->get('env(enum:'.StringBackedEnum::class.':foo)'),
+            $bag->get('env(Bar)'),
+        ]);
+
+        $expected = [
+            'enum:Symfony\Component\DependencyInjection\Tests\Fixtures\StringBackedEnum:foo' => 1,
+            'Bar' => 1,
+        ];
+
+        $this->assertSame($expected, $config->getEnvCounters());
+    }
+
     public function testCreateServiceWithAbstractArgument()
     {
         $this->expectException(RuntimeException::class);