diff --git a/lib/private/L10N/Factory.php b/lib/private/L10N/Factory.php
index e277a00e653d5..dee15b0d84383 100644
--- a/lib/private/L10N/Factory.php
+++ b/lib/private/L10N/Factory.php
@@ -126,6 +126,11 @@ public function get($app, $lang = null) {
 	 * @return string language If nothing works it returns 'en'
 	 */
 	public function findLanguage($app = null) {
+		$forceLang = $this->config->getSystemValue('force_language', false);
+		if (is_string($forceLang)) {
+			$this->requestLanguage = $forceLang;
+		}
+
 		if ($this->requestLanguage !== '' && $this->languageExists($app, $this->requestLanguage)) {
 			return $this->requestLanguage;
 		}
diff --git a/tests/lib/L10N/FactoryTest.php b/tests/lib/L10N/FactoryTest.php
index 602967b162620..38d52d7763b32 100644
--- a/tests/lib/L10N/FactoryTest.php
+++ b/tests/lib/L10N/FactoryTest.php
@@ -110,7 +110,12 @@ public function testFindLanguageWithNotExistingRequestLanguageAndExistingStoredU
 				->with('MyApp', 'de')
 				->willReturn(false);
 		$this->config
-			->expects($this->once())
+			->expects($this->at(0))
+			->method('getSystemValue')
+			->with('force_language', false)
+			->willReturn(false);
+		$this->config
+			->expects($this->at(1))
 			->method('getSystemValue')
 			->with('installed', false)
 			->willReturn(true);
@@ -144,7 +149,12 @@ public function testFindLanguageWithNotExistingRequestLanguageAndNotExistingStor
 				->with('MyApp', 'de')
 				->willReturn(false);
 		$this->config
-				->expects($this->at(0))
+			->expects($this->at(0))
+			->method('getSystemValue')
+			->with('force_language', false)
+			->willReturn(false);
+		$this->config
+				->expects($this->at(1))
 				->method('getSystemValue')
 				->with('installed', false)
 				->willReturn(true);
@@ -167,7 +177,7 @@ public function testFindLanguageWithNotExistingRequestLanguageAndNotExistingStor
 				->with('MyApp', 'jp')
 				->willReturn(false);
 		$this->config
-				->expects($this->at(2))
+				->expects($this->at(3))
 				->method('getSystemValue')
 				->with('default_language', false)
 				->willReturn('es');
@@ -187,7 +197,12 @@ public function testFindLanguageWithNotExistingRequestLanguageAndNotExistingStor
 				->with('MyApp', 'de')
 				->willReturn(false);
 		$this->config
-				->expects($this->at(0))
+			->expects($this->at(0))
+			->method('getSystemValue')
+			->with('force_language', false)
+			->willReturn(false);
+		$this->config
+				->expects($this->at(1))
 				->method('getSystemValue')
 				->with('installed', false)
 				->willReturn(true);
@@ -210,7 +225,7 @@ public function testFindLanguageWithNotExistingRequestLanguageAndNotExistingStor
 				->with('MyApp', 'jp')
 				->willReturn(false);
 		$this->config
-				->expects($this->at(2))
+				->expects($this->at(3))
 				->method('getSystemValue')
 				->with('default_language', false)
 				->willReturn('es');
@@ -233,7 +248,12 @@ public function testFindLanguageWithNotExistingRequestLanguageAndNotExistingStor
 				->with('MyApp', 'de')
 				->willReturn(false);
 		$this->config
-				->expects($this->at(0))
+			->expects($this->at(0))
+			->method('getSystemValue')
+			->with('force_language', false)
+			->willReturn(false);
+		$this->config
+				->expects($this->at(1))
 				->method('getSystemValue')
 				->with('installed', false)
 				->willReturn(true);
@@ -256,7 +276,7 @@ public function testFindLanguageWithNotExistingRequestLanguageAndNotExistingStor
 				->with('MyApp', 'jp')
 				->willReturn(false);
 		$this->config
-				->expects($this->at(2))
+				->expects($this->at(3))
 				->method('getSystemValue')
 				->with('default_language', false)
 				->willReturn('es');
@@ -273,6 +293,22 @@ public function testFindLanguageWithNotExistingRequestLanguageAndNotExistingStor
 		$this->assertSame('en', $factory->findLanguage('MyApp'));
 	}
 
+	public function testFindLanguageWithForcedLanguage() {
+		$factory = $this->getFactory(['languageExists']);
+		$this->config
+			->expects($this->at(0))
+			->method('getSystemValue')
+			->with('force_language', false)
+			->willReturn('de');
+
+		$factory->expects($this->once())
+			->method('languageExists')
+			->with('MyApp', 'de')
+			->willReturn(true);
+
+		$this->assertSame('de', $factory->findLanguage('MyApp'));
+	}
+
 	/**
 	 * @dataProvider dataFindAvailableLanguages
 	 *