diff --git a/src/Symfony/Component/DependencyInjection/Compiler/ServiceLocatorTagPass.php b/src/Symfony/Component/DependencyInjection/Compiler/ServiceLocatorTagPass.php
index 96d4bbe0f4..ad2cbefd25 100644
--- a/src/Symfony/Component/DependencyInjection/Compiler/ServiceLocatorTagPass.php
+++ b/src/Symfony/Component/DependencyInjection/Compiler/ServiceLocatorTagPass.php
@@ -52,6 +52,8 @@ final class ServiceLocatorTagPass extends AbstractRecursivePass
             throw new InvalidArgumentException(sprintf('Invalid definition for service "%s": an array of references is expected as first argument when the "container.service_locator" tag is set.', $this->currentId));
         }
 
+        $i = 0;
+
         foreach ($arguments[0] as $k => $v) {
             if ($v instanceof ServiceClosureArgument) {
                 continue;
@@ -60,10 +62,13 @@ final class ServiceLocatorTagPass extends AbstractRecursivePass
                 throw new InvalidArgumentException(sprintf('Invalid definition for service "%s": an array of references is expected as first argument when the "container.service_locator" tag is set, "%s" found for key "%s".', $this->currentId, \is_object($v) ? \get_class($v) : \gettype($v), $k));
             }
 
-            if (\is_int($k)) {
+            if ($i === $k) {
                 unset($arguments[0][$k]);
 
                 $k = (string) $v;
+                ++$i;
+            } elseif (\is_int($k)) {
+                $i = null;
             }
             $arguments[0][$k] = new ServiceClosureArgument($v);
         }
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Compiler/ServiceLocatorTagPassTest.php b/src/Symfony/Component/DependencyInjection/Tests/Compiler/ServiceLocatorTagPassTest.php
index 1de02d2577..66af69b543 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Compiler/ServiceLocatorTagPassTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Compiler/ServiceLocatorTagPassTest.php
@@ -114,6 +114,7 @@ class ServiceLocatorTagPassTest extends TestCase
             ->setArguments([[
                 'bar' => new Reference('baz'),
                 new Reference('bar'),
+                16 => new Reference('baz'),
             ]])
             ->addTag('container.service_locator')
         ;
@@ -124,6 +125,7 @@ class ServiceLocatorTagPassTest extends TestCase
         $locator = $container->get('foo');
 
         $this->assertSame(TestDefinition1::class, \get_class($locator('bar')));
+        $this->assertSame(TestDefinition2::class, \get_class($locator(16)));
     }
 
     public function testBindingsAreCopied()