diff --git a/wp-includes/general-template.php b/wp-includes/general-template.php
index 97468acf2a..687ee25f49 100644
--- a/wp-includes/general-template.php
+++ b/wp-includes/general-template.php
@@ -888,12 +888,27 @@ function get_custom_logo( $blog_id = 0 ) {
 
 	// We have a logo. Logo is go.
 	if ( $custom_logo_id ) {
+		$custom_logo_attr = array(
+			'class'    => 'custom-logo',
+			'itemprop' => 'logo',
+		);
+
+		/*
+		 * If the logo alt attribute is empty, get the site title and explicitly
+		 * pass it to the attributes used by wp_get_attachment_image().
+		 */
+		$image_alt = get_post_meta( $custom_logo_id, '_wp_attachment_image_alt', true );
+		if ( empty( $image_alt ) ) {
+			$custom_logo_attr['alt'] = get_bloginfo( 'name', 'display' );
+		}
+
+		/*
+		 * If the alt attribute is not empty, there's no need to explicitly pass
+		 * it because wp_get_attachment_image() already adds the alt attribute.
+		 */
 		$html = sprintf( '<a href="%1$s" class="custom-logo-link" rel="home" itemprop="url">%2$s</a>',
 			esc_url( home_url( '/' ) ),
-			wp_get_attachment_image( $custom_logo_id, 'full', false, array(
-				'class'    => 'custom-logo',
-				'itemprop' => 'logo',
-			) )
+			wp_get_attachment_image( $custom_logo_id, 'full', false, $custom_logo_attr )
 		);
 	}
 
diff --git a/wp-includes/version.php b/wp-includes/version.php
index fe90f2a5be..610f646fc0 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.8-beta1-40816';
+$wp_version = '4.8-beta1-40817';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.