diff --git a/DependencyInjection/BazingaJsTranslationExtension.php b/DependencyInjection/BazingaJsTranslationExtension.php
index 2859b28a..a3b84c98 100644
--- a/DependencyInjection/BazingaJsTranslationExtension.php
+++ b/DependencyInjection/BazingaJsTranslationExtension.php
@@ -32,11 +32,6 @@ public function load(array $configs, ContainerBuilder $container): void
             ->replaceArgument(6, $config['default_domain'])
             ->replaceArgument(7, $config['http_cache_time']);
 
-        // Add fallback locale to active locales if missing
-        if ($config['active_locales'] && !in_array($config['locale_fallback'], $config['active_locales'])) {
-            array_push($config['active_locales'], $config['locale_fallback']);
-        }
-
         $container
             ->getDefinition('bazinga.jstranslation.translation_dumper')
             ->replaceArgument(3, $config['locale_fallback'])
diff --git a/Dumper/TranslationDumper.php b/Dumper/TranslationDumper.php
index f5d8d0ff..7b5856a5 100644
--- a/Dumper/TranslationDumper.php
+++ b/Dumper/TranslationDumper.php
@@ -79,6 +79,10 @@ public function __construct(
         $this->filesystem     = $filesystem;
         $this->localeFallback = $localeFallback;
         $this->defaultDomain  = $defaultDomain;
+        // Add fallback locale to active locales if missing
+        if ($activeLocales && !in_array($localeFallback, $activeLocales)) {
+            array_push($activeLocales, $localeFallback);
+        }
         $this->activeLocales  = $activeLocales;
         $this->activeDomains  = $activeDomains;
     }
diff --git a/Tests/Dumper/TranslationDumperFallbackLocaleTest.php b/Tests/Dumper/TranslationDumperFallbackLocaleTest.php
new file mode 100644
index 00000000..04609bc2
--- /dev/null
+++ b/Tests/Dumper/TranslationDumperFallbackLocaleTest.php
@@ -0,0 +1,43 @@
+<?php
+
+namespace Bazinga\Bundle\JsTranslationBundle\Tests\Dumper;
+
+use Bazinga\Bundle\JsTranslationBundle\Dumper\TranslationDumper;
+use Bazinga\Bundle\JsTranslationBundle\Finder\TranslationFinder;
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Filesystem\Filesystem;
+use Twig\Environment;
+
+class TranslationDumperFallbackLocaleTest extends TestCase
+{
+    private function createDumper(string $localeFallback, array $activeLocales): TranslationDumper
+    {
+        $twig = $this->createMock(Environment::class);
+        $finder = $this->createMock(TranslationFinder::class);
+        $filesystem = $this->createMock(Filesystem::class);
+
+        return new TranslationDumper($twig, $finder, $filesystem, $localeFallback, 'messages', $activeLocales);
+    }
+
+    public function testFallbackLocaleIsAddedToActiveLocalesWhenMissing()
+    {
+        $dumper = $this->createDumper('en', ['fr']);
+
+        $this->assertContains('en', $dumper->getActiveLocales());
+        $this->assertContains('fr', $dumper->getActiveLocales());
+    }
+
+    public function testFallbackLocaleIsNotDuplicatedWhenAlreadyPresent()
+    {
+        $dumper = $this->createDumper('en', ['fr', 'en']);
+
+        $this->assertEquals(['fr', 'en'], $dumper->getActiveLocales());
+    }
+
+    public function testFallbackLocaleIsNotAddedWhenActiveLocalesIsEmpty()
+    {
+        $dumper = $this->createDumper('en', []);
+
+        $this->assertEmpty($dumper->getActiveLocales());
+    }
+}
diff --git a/Tests/Fixtures/app/config/base_config.yml b/Tests/Fixtures/app/config/base_config.yml
index 25fb855e..35b1ee0a 100644
--- a/Tests/Fixtures/app/config/base_config.yml
+++ b/Tests/Fixtures/app/config/base_config.yml
@@ -15,7 +15,7 @@ twig:
 bazinga_js_translation:
     active_locales:
         - fr
-        - en
+    locale_fallback: en
     active_domains:
         - messages
         - numerics