diff --git a/src/Symfony/Bundle/FrameworkBundle/Command/ConfigDebugCommand.php b/src/Symfony/Bundle/FrameworkBundle/Command/ConfigDebugCommand.php
index e88de6e31f257..8a8f2355b0365 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Command/ConfigDebugCommand.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Command/ConfigDebugCommand.php
@@ -13,6 +13,8 @@
 
 use Symfony\Component\Config\Definition\ConfigurationInterface;
 use Symfony\Component\Config\Definition\Processor;
+use Symfony\Component\Console\Completion\CompletionInput;
+use Symfony\Component\Console\Completion\CompletionSuggestions;
 use Symfony\Component\Console\Exception\LogicException;
 use Symfony\Component\Console\Input\InputArgument;
 use Symfony\Component\Console\Input\InputInterface;
@@ -94,11 +96,7 @@ protected function execute(InputInterface $input, OutputInterface $output): int
         $extensionAlias = $extension->getAlias();
         $container = $this->compileContainer();
 
-        $config = $container->resolveEnvPlaceholders(
-            $container->getParameterBag()->resolveValue(
-                $this->getConfigForExtension($extension, $container)
-            )
-        );
+        $config = $this->getConfig($extension, $container);
 
         if (null === $path = $input->getArgument('path')) {
             $io->title(
@@ -188,4 +186,55 @@ private function getConfigForExtension(ExtensionInterface $extension, ContainerB
 
         return (new Processor())->processConfiguration($configuration, $configs);
     }
+
+    public function complete(CompletionInput $input, CompletionSuggestions $suggestions): void
+    {
+        if ($input->mustSuggestArgumentValuesFor('name')) {
+            $suggestions->suggestValues($this->getAvailableBundles(!preg_match('/^[A-Z]/', $input->getCompletionValue())));
+
+            return;
+        }
+
+        if ($input->mustSuggestArgumentValuesFor('path') && null !== $name = $input->getArgument('name')) {
+            try {
+                $config = $this->getConfig($this->findExtension($name), $this->compileContainer());
+                $paths = array_keys(self::buildPathsCompletion($config));
+                $suggestions->suggestValues($paths);
+            } catch (LogicException $e) {
+            }
+        }
+    }
+
+    private function getAvailableBundles(bool $alias): array
+    {
+        $availableBundles = [];
+        foreach ($this->getApplication()->getKernel()->getBundles() as $bundle) {
+            $availableBundles[] = $alias ? $bundle->getContainerExtension()->getAlias() : $bundle->getName();
+        }
+
+        return $availableBundles;
+    }
+
+    private function getConfig(ExtensionInterface $extension, ContainerBuilder $container)
+    {
+        return $container->resolveEnvPlaceholders(
+            $container->getParameterBag()->resolveValue(
+                $this->getConfigForExtension($extension, $container)
+            )
+        );
+    }
+
+    private static function buildPathsCompletion(array $paths, string $prefix = ''): array
+    {
+        $completionPaths = [];
+        foreach ($paths as $key => $values) {
+            if (\is_array($values)) {
+                $completionPaths = $completionPaths + self::buildPathsCompletion($values, $prefix.$key.'.');
+            } else {
+                $completionPaths[$prefix.$key] = null;
+            }
+        }
+
+        return $completionPaths;
+    }
 }
diff --git a/src/Symfony/Bundle/FrameworkBundle/Tests/Functional/ConfigDebugCommandTest.php b/src/Symfony/Bundle/FrameworkBundle/Tests/Functional/ConfigDebugCommandTest.php
index 0df853997c59a..8135f4dcfe419 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Tests/Functional/ConfigDebugCommandTest.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Tests/Functional/ConfigDebugCommandTest.php
@@ -11,9 +11,11 @@
 
 namespace Symfony\Bundle\FrameworkBundle\Tests\Functional;
 
+use Symfony\Bundle\FrameworkBundle\Command\ConfigDebugCommand;
 use Symfony\Bundle\FrameworkBundle\Console\Application;
 use Symfony\Component\Console\Input\ArrayInput;
 use Symfony\Component\Console\Output\NullOutput;
+use Symfony\Component\Console\Tester\CommandCompletionTester;
 use Symfony\Component\Console\Tester\CommandTester;
 
 /**
@@ -111,6 +113,31 @@ public function testDumpThrowsExceptionWhenDefaultConfigFallbackIsImpossible()
         $tester->execute(['name' => 'ExtensionWithoutConfigTestBundle']);
     }
 
+    /**
+     * @dataProvider provideCompletionSuggestions
+     */
+    public function testComplete(array $input, array $expectedSuggestions)
+    {
+        $this->application->add(new ConfigDebugCommand());
+
+        $tester = new CommandCompletionTester($this->application->get('debug:config'));
+
+        $suggestions = $tester->complete($input);
+
+        foreach ($expectedSuggestions as $expectedSuggestion) {
+            $this->assertContains($expectedSuggestion, $suggestions);
+        }
+    }
+
+    public function provideCompletionSuggestions(): \Generator
+    {
+        yield 'name' => [[''], ['default_config_test', 'extension_without_config_test', 'framework', 'test']];
+
+        yield 'name (started CamelCase)' => [['Fra'], ['DefaultConfigTestBundle', 'ExtensionWithoutConfigTestBundle', 'FrameworkBundle', 'TestBundle']];
+
+        yield 'name with existing path' => [['framework', ''], ['secret', 'router.resource', 'router.utf8', 'router.enabled', 'validation.enabled', 'default_locale']];
+    }
+
     private function createCommandTester(): CommandTester
     {
         $command = $this->application->find('debug:config');