diff --git a/api/ApiULSLocalization.php b/api/ApiULSLocalization.php
index dc13607a..2b618250 100644
--- a/api/ApiULSLocalization.php
+++ b/api/ApiULSLocalization.php
@@ -30,7 +30,11 @@ class ApiULSLocalization extends ApiBase {
 		$params = $this->extractRequestParams();
 		$language = $params['language'];
 		if ( !Language::isValidCode( $language ) ) {
-			$this->dieUsage( 'Invalid language', 'invalidlanguage' );
+			if ( is_callable( [ $this, 'dieWithError' ] ) ) {
+				$this->dieWithError( [ 'apierror-invalidlang', 'language' ], 'invalidlanguage' );
+			} else {
+				$this->dieUsage( 'Invalid language', 'invalidlanguage' );
+			}
 		}
 		$contents = ULSJsonMessageLoader::getMessages( $language );
 		// Output the file's contents raw