diff --git a/config/config.sample.php b/config/config.sample.php
index 14e093600b..5a79140dfb 100644
--- a/config/config.sample.php
+++ b/config/config.sample.php
@@ -157,7 +157,11 @@ $CONFIG = array(
  * language codes such as ``en`` for English, ``de`` for German, and ``fr`` for
  * French. It overrides automatic language detection on public pages like login
  * or shared items. User's language preferences configured under "personal ->
- * language" override this setting after they have logged in.
+ * language" override this setting after they have logged in. Nextcloud has two
+ * distinguished language codes for German, 'de' and 'de_DE'. 'de' is used for
+ * informal German and 'de_DE' for formal German. By setting this value to 'de_DE'
+ * you can enforce the formal version of German unless the user has chosen
+ * something different explicitly.
  *
  * Defaults to ``en``
  */
diff --git a/lib/private/L10N/Factory.php b/lib/private/L10N/Factory.php
index 399bebb818..e277a00e65 100644
--- a/lib/private/L10N/Factory.php
+++ b/lib/private/L10N/Factory.php
@@ -260,7 +260,7 @@ class Factory implements IFactory {
 
 				foreach ($available as $available_language) {
 					if ($preferred_language === strtolower($available_language)) {
-						return $available_language;
+						return $this->respectDefaultLanguage($app, $available_language);
 					}
 				}
 
@@ -276,6 +276,31 @@ class Factory implements IFactory {
 		throw new LanguageNotFoundException();
 	}
 
+	/**
+	 * if default language is set to de_DE (formal German) this should be
+	 * preferred to 'de' (non-formal German) if possible
+	 *
+	 * @param string|null $app
+	 * @param string $lang
+	 * @return string
+	 */
+	protected function respectDefaultLanguage($app, $lang) {
+		$result = $lang;
+		$defaultLanguage = $this->config->getSystemValue('default_language', false);
+
+		// use formal version of german ("Sie" instead of "Du") if the default
+		// language is set to 'de_DE' if possible
+		if (is_string($defaultLanguage) &&
+			strtolower($lang) === 'de' &&
+			strtolower($defaultLanguage) === 'de_de' &&
+			$this->languageExists($app, 'de_DE')
+		) {
+			$result = 'de_DE';
+		}
+
+		return $result;
+	}
+
 	/**
 	 * Checks if $sub is a subdirectory of $parent
 	 *
diff --git a/tests/lib/L10N/FactoryTest.php b/tests/lib/L10N/FactoryTest.php
index 171be67d33..602967b162 100644
--- a/tests/lib/L10N/FactoryTest.php
+++ b/tests/lib/L10N/FactoryTest.php
@@ -368,12 +368,17 @@ class FactoryTest extends TestCase {
 	 * @param string $expected
 	 */
 	public function testGetLanguageFromRequest($app, $header, array $availableLanguages, $expected) {
-		$factory = $this->getFactory(['findAvailableLanguages']);
+		$factory = $this->getFactory(['findAvailableLanguages', 'respectDefaultLanguage']);
 		$factory->expects($this->once())
 			->method('findAvailableLanguages')
 			->with($app)
 			->willReturn($availableLanguages);
 
+		$factory->expects($this->any())
+			->method('respectDefaultLanguage')->willReturnCallback(function($app, $lang) {
+				return $lang;
+			});
+
 		$this->request->expects($this->once())
 			->method('getHeader')
 			->with('ACCEPT_LANGUAGE')
@@ -497,7 +502,7 @@ class FactoryTest extends TestCase {
 			->with($this->equalTo('ACCEPT_LANGUAGE'))
 			->willReturn($browserLang);
 
-		$factory = $this->getFactory(['languageExists', 'findAvailableLanguages']);
+		$factory = $this->getFactory(['languageExists', 'findAvailableLanguages', 'respectDefaultLanguage']);
 		$factory->expects($this->any())
 			->method('languageExists')
 			->will($this->returnCallback(function ($app, $lang) use ($availableLang) {
@@ -508,9 +513,44 @@ class FactoryTest extends TestCase {
 			->will($this->returnCallback(function ($app) use ($availableLang) {
 				return $availableLang;
 			}));
+		$factory->expects($this->any())
+			->method('respectDefaultLanguage')->willReturnCallback(function($app, $lang) {
+			return $lang;
+			});
 
 		$lang = $factory->findLanguage(null);
 		$this->assertSame($expected, $lang);
 
 	}
+
+	public function dataTestRespectDefaultLanguage() {
+		return [
+			['de', 'de_DE', true, 'de_DE'],
+			['de', 'de', true, 'de'],
+			['de', false, true, 'de'],
+			['fr', 'de_DE', true, 'fr'],
+		];
+	}
+
+	/**
+	 * test if we respect default language if possible
+	 *
+	 * @dataProvider dataTestRespectDefaultLanguage
+	 *
+	 * @param string $lang
+	 * @param string $defaultLanguage
+	 * @param bool $langExists
+	 * @param string $expected
+	 */
+	public function testRespectDefaultLanguage($lang, $defaultLanguage, $langExists, $expected) {
+		$factory = $this->getFactory(['languageExists']);
+		$factory->expects($this->any())
+			->method('languageExists')->willReturn($langExists);
+		$this->config->expects($this->any())
+			->method('getSystemValue')->with('default_language', false)->willReturn($defaultLanguage);
+
+		$result = $this->invokePrivate($factory, 'respectDefaultLanguage', ['app', $lang]);
+		$this->assertSame($expected, $result);
+	}
+
 }