diff --git a/lib/private/App/AppManager.php b/lib/private/App/AppManager.php
index 6b819ef7ac..6c1f5ba694 100644
--- a/lib/private/App/AppManager.php
+++ b/lib/private/App/AppManager.php
@@ -32,6 +32,7 @@
 namespace OC\App;
 
 use OCP\App\AppPathNotFoundException;
+use OC_App;
 use OCP\App\IAppManager;
 use OCP\App\ManagerEvent;
 use OCP\IAppConfig;
@@ -210,8 +211,12 @@ class AppManager implements IAppManager {
 	 * Enable an app for every user
 	 *
 	 * @param string $appId
+	 * @throws \Exception
 	 */
 	public function enableApp($appId) {
+		if(OC_App::getAppPath($appId) === false) {
+			throw new \Exception("$appId can't be enabled since it is not installed.");
+		}
 		$this->installedAppsCache[$appId] = 'yes';
 		$this->appConfig->setValue($appId, 'enabled', 'yes');
 		$this->dispatcher->dispatch(ManagerEvent::EVENT_APP_ENABLE, new ManagerEvent(
diff --git a/tests/lib/App/ManagerTest.php b/tests/lib/App/ManagerTest.php
index e38f72b3d9..8b23168938 100644
--- a/tests/lib/App/ManagerTest.php
+++ b/tests/lib/App/ManagerTest.php
@@ -116,16 +116,33 @@ class ManagerTest extends TestCase {
 
 	public function testEnableApp() {
 		$this->expectClearCache();
-		$this->manager->enableApp('test');
-		$this->assertEquals('yes', $this->appConfig->getValue('test', 'enabled', 'no'));
+		// making sure "files_trashbin" is disabled
+		if ($this->manager->isEnabledForUser('files_trashbin')) {
+			$this->manager->disableApp('files_trashbin');
+		}
+		$this->manager->enableApp('files_trashbin');
+		$this->assertEquals('yes', $this->appConfig->getValue('files_trashbin', 'enabled', 'no'));
 	}
 
 	public function testDisableApp() {
 		$this->expectClearCache();
-		$this->manager->disableApp('test');
-		$this->assertEquals('no', $this->appConfig->getValue('test', 'enabled', 'no'));
+		$this->manager->disableApp('files_trashbin');
+		$this->assertEquals('no', $this->appConfig->getValue('files_trashbin', 'enabled', 'no'));
 	}
 
+	public function testNotEnableIfNotInstalled() {
+		try {
+			$this->manager->enableApp('some_random_name_which_i_hope_is_not_an_app');
+			$this->assertFalse(true, 'If this line is reached the expected exception is not thrown.');
+		} catch (\Exception $e) {
+			// excpetion is expected
+			$this->assertEquals("some_random_name_which_i_hope_is_not_an_app can't be enabled since it is not installed.", $e->getMessage());
+		}
+		$this->assertEquals('no', $this->appConfig->getValue(
+			'some_random_name_which_i_hope_is_not_an_app', 'enabled', 'no'
+		));
+  	}
+
 	public function testEnableAppForGroups() {
 		$groups = array(
 			new Group('group1', array(), null),