diff --git a/src/wp-includes/class-wp-oembed-controller.php b/src/wp-includes/class-wp-oembed-controller.php
index 22c062be9f..a613d0616d 100644
--- a/src/wp-includes/class-wp-oembed-controller.php
+++ b/src/wp-includes/class-wp-oembed-controller.php
@@ -32,7 +32,7 @@ final class WP_oEmbed_Controller {
 
 		if ( false === $wp_query->get( 'url', false ) ) {
 			status_header( 400 );
-			echo 'URL parameter missing';
+			return get_status_header_desc( 400 );
 			exit;
 		}
 
@@ -88,7 +88,7 @@ final class WP_oEmbed_Controller {
 
 		if ( false === $data ) {
 			status_header( 404 );
-			return __( 'Invalid URL.' );
+			return get_status_header_desc( 404 );
 		}
 
 		if ( 'json' === $request['format'] ) {
@@ -117,7 +117,7 @@ final class WP_oEmbed_Controller {
 		// Bail if the result couldn't be JSON encoded.
 		if ( ! $result || ! is_array( $data ) || empty( $data ) ) {
 			status_header( 501 );
-			return 'Not implemented';
+			return get_status_header_desc( 501 );
 		}
 
 		if ( ! headers_sent() ) {
diff --git a/tests/phpunit/tests/oembed/controller.php b/tests/phpunit/tests/oembed/controller.php
index 34ce7dd4ee..51c6302c32 100644
--- a/tests/phpunit/tests/oembed/controller.php
+++ b/tests/phpunit/tests/oembed/controller.php
@@ -13,7 +13,7 @@ class Test_oEmbed_Controller extends WP_UnitTestCase {
 
 		$legacy_controller = new WP_oEmbed_Controller();
 
-		$this->assertEquals( 'Invalid URL.', $legacy_controller->dispatch( $request ) );
+		$this->assertEquals( get_status_header_desc( 404 ), $legacy_controller->dispatch( $request ) );
 	}
 
 	function test_request_json() {
@@ -27,7 +27,7 @@ class Test_oEmbed_Controller extends WP_UnitTestCase {
 
 		// WP_Query arguments.
 		$request = array(
-			'url'	  => get_permalink( $post->ID ),
+			'url'      => get_permalink( $post->ID ),
 			'format'   => 'json',
 			'maxwidth' => 400,
 			'callback' => '',
@@ -69,7 +69,7 @@ class Test_oEmbed_Controller extends WP_UnitTestCase {
 		) );
 
 		$request = array(
-			'url'	  => get_permalink( $post->ID ),
+			'url'      => get_permalink( $post->ID ),
 			'format'   => 'json',
 			'maxwidth' => 600,
 			'callback' => 'mycallback',
@@ -92,7 +92,7 @@ class Test_oEmbed_Controller extends WP_UnitTestCase {
 		) );
 
 		$request = array(
-			'url'	  => get_permalink( $post->ID ),
+			'url'      => get_permalink( $post->ID ),
 			'format'   => 'json',
 			'maxwidth' => 600,
 			'callback' => array( 'foo', 'bar' ),
@@ -112,9 +112,9 @@ class Test_oEmbed_Controller extends WP_UnitTestCase {
 
 		$legacy_controller = new WP_oEmbed_Controller();
 
-		$this->assertEquals( 'Not implemented',  $legacy_controller->json_response( null, $request ) );
-		$this->assertEquals( 'Not implemented',  $legacy_controller->json_response( 123, $request ) );
-		$this->assertEquals( 'Not implemented',  $legacy_controller->json_response( array(), $request ) );
+		$this->assertEquals( get_status_header_desc( 501 ), $legacy_controller->json_response( null, $request ) );
+		$this->assertEquals( get_status_header_desc( 501 ), $legacy_controller->json_response( 123, $request ) );
+		$this->assertEquals( get_status_header_desc( 501 ), $legacy_controller->json_response( array(), $request ) );
 	}
 
 	function test_request_xml() {