diff --git a/src/web/ResponseBehavior.php b/src/web/ResponseBehavior.php
index d614867..a229783 100644
--- a/src/web/ResponseBehavior.php
+++ b/src/web/ResponseBehavior.php
@@ -4,6 +4,8 @@
 
 use Craft;
 use craft\cloud\fs\TmpFs;
+use craft\cloud\HeaderEnum;
+use craft\cloud\Module;
 use craft\web\Response;
 use Illuminate\Support\Collection;
 use yii\base\Behavior;
@@ -40,6 +42,7 @@ public function gzip(): void
 
     public function afterPrepare(Event $event): void
     {
+        $this->addDevModeHeader();
         $this->joinMultiValueHeaders();
         $this->gzip();
         $this->serveBinaryFromS3();
@@ -111,4 +114,11 @@ protected function joinHeaderValues(string $name, array $values, string $glue):
 
         return $value;
     }
+
+    protected function addDevModeHeader(): void
+    {
+        if (Module::getInstance()->getConfig()->getDevMode()) {
+            $this->owner->getHeaders()->set(HeaderEnum::DEV_MODE->value, '1');
+        }
+    }
 }