diff --git a/wp-includes/media.php b/wp-includes/media.php
index ade1114d16..8965da9ac2 100644
--- a/wp-includes/media.php
+++ b/wp-includes/media.php
@@ -1560,6 +1560,8 @@ function img_caption_shortcode( $attr, $content = null ) {
 		return $content;
 	}
 
+	$id = $caption_id = $describedby = '';
+
 	if ( $atts['id'] ) {
 		$atts['id'] = sanitize_html_class( $atts['id'] );
 		$id         = 'id="' . esc_attr( $atts['id'] ) . '" ';
@@ -1571,8 +1573,6 @@ function img_caption_shortcode( $attr, $content = null ) {
 		$atts['caption_id'] = 'caption-' . str_replace( '_', '-', $atts['id'] );
 	}
 
-	$describedby = '';
-
 	if ( $atts['caption_id'] ) {
 		$caption_id  = 'id="' . esc_attr( $atts['caption_id'] ) . '" ';
 		$describedby = 'aria-describedby="' . esc_attr( $atts['caption_id'] ) . '" ';
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 2532b874e3..a281dab794 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.0-alpha-42705';
+$wp_version = '5.0-alpha-42706';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.