diff --git a/src/MergePlugin.php b/src/MergePlugin.php
index a9af5b6..e235417 100644
--- a/src/MergePlugin.php
+++ b/src/MergePlugin.php
@@ -20,6 +20,7 @@
 use Composer\Installer\PackageEvents;
 use Composer\IO\IOInterface;
 use Composer\Package\RootPackageInterface;
+use Composer\Plugin\CommandEvent;
 use Composer\Plugin\PluginEvents;
 use Composer\Plugin\PluginInterface;
 use Composer\Script\Event as ScriptEvent;
@@ -155,6 +156,8 @@ public static function getSubscribedEvents()
         return [
             PluginEvents::INIT =>
                 ['onInit', self::CALLBACK_PRIORITY],
+            PluginEvents::COMMAND =>
+                ['onCommand', self::CALLBACK_PRIORITY],
             PackageEvents::POST_PACKAGE_INSTALL =>
                 ['onPostPackageInstall', self::CALLBACK_PRIORITY],
             ScriptEvents::POST_INSTALL_CMD =>
@@ -197,6 +200,21 @@ public function onInit(BaseEvent $event)
         $this->mergeFiles($this->state->getRequires(), true);
     }
 
+    /**
+     * @param \Composer\Plugin\CommandEvent $event
+     *
+     * @return void
+     */
+    public function onCommand(CommandEvent $event)
+    {
+        if ($event->getCommandName() == 'depends') {
+            // This command needs to know about dev dependencies.
+            $this->state->setDevMode(true);
+            $this->mergeFiles($this->state->getIncludes());
+            $this->mergeFiles($this->state->getRequires(), true);
+        }
+    }
+
     /**
      * Handle an event callback for an install, update or dump command by
      * checking for "merge-plugin" in the "extra" data and merging package
diff --git a/tests/phpunit/MergePluginTest.php b/tests/phpunit/MergePluginTest.php
index 8fff0ea..13290fd 100644
--- a/tests/phpunit/MergePluginTest.php
+++ b/tests/phpunit/MergePluginTest.php
@@ -81,9 +81,10 @@ public function testSubscribedEvents()
     {
         $subscriptions = MergePlugin::getSubscribedEvents();
 
-        $this->assertCount(7, $subscriptions);
+        $this->assertCount(8, $subscriptions);
 
         $this->assertArrayHasKey(PluginEvents::INIT, $subscriptions);
+        $this->assertArrayHasKey(PluginEvents::COMMAND, $subscriptions);
         $this->assertArrayHasKey(ScriptEvents::PRE_INSTALL_CMD, $subscriptions);
         $this->assertArrayHasKey(ScriptEvents::PRE_UPDATE_CMD, $subscriptions);
         $this->assertArrayHasKey(ScriptEvents::PRE_AUTOLOAD_DUMP, $subscriptions);