diff --git a/lib/private/L10N/L10N.php b/lib/private/L10N/L10N.php
index d0794c9c9c06f..ea4aa0527bba9 100644
--- a/lib/private/L10N/L10N.php
+++ b/lib/private/L10N/L10N.php
@@ -215,7 +215,12 @@ public function getTranslations(): array {
 	public function getIdentityTranslator(): IdentityTranslator {
 		if (\is_null($this->identityTranslator)) {
 			$this->identityTranslator = new IdentityTranslator();
-			$this->identityTranslator->setLocale($this->getLocaleCode());
+			// We need to use the language code here instead of the locale,
+			// because Symfony does not distinguish between the two and would
+			// otherwise e.g. with locale "Czech" and language "German" try to
+			// pick a non-existing plural rule, because Czech has 4 plural forms
+			// and German only 2.
+			$this->identityTranslator->setLocale($this->getLanguageCode());
 		}
 
 		return $this->identityTranslator;
diff --git a/tests/lib/L10N/L10nTest.php b/tests/lib/L10N/L10nTest.php
index f224592432c98..67ad58435461b 100644
--- a/tests/lib/L10N/L10nTest.php
+++ b/tests/lib/L10N/L10nTest.php
@@ -85,6 +85,15 @@ public function testCzechPluralTranslations() {
 		$this->assertEquals('5 oken', (string)$l->n('%n window', '%n windows', 5));
 	}
 
+	public function testGermanPluralWithCzechLocaleTranslations() {
+		$transFile = \OC::$SERVERROOT.'/tests/data/l10n/de.json';
+		$l = new L10N($this->getFactory(), 'test', 'de', 'cs_CZ', [$transFile]);
+
+		$this->assertEquals('1 Datei', (string) $l->n('%n file', '%n files', 1));
+		$this->assertEquals('2 Dateien', (string) $l->n('%n file', '%n files', 2));
+		$this->assertEquals('5 Dateien', (string) $l->n('%n file', '%n files', 5));
+	}
+
 	public function dataPlaceholders(): array {
 		return [
 			['Ordered placeholders one %s two %s', 'Placeholder one 1 two 2'],