diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php
index 3ec49867ce..61fb044254 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php
@@ -1041,8 +1041,10 @@ class WP_REST_Comments_Controller extends WP_REST_Controller {
 			$prepared_comment['comment_author_IP'] = $request['author_ip'];
 		}
 
-		if ( isset( $request['author_user_agent'] ) ) {
+		if ( ! empty( $request['author_user_agent'] ) ) {
 			$prepared_comment['comment_agent'] = $request['author_user_agent'];
+		} elseif ( $request->get_header( 'user_agent' ) ) {
+			$prepared_comment['comment_agent'] = $request->get_header( 'user_agent' );
 		}
 
 		if ( isset( $request['type'] ) ) {
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 329cacbeb6..bcfc3dbee1 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.7-beta4-39286';
+$wp_version = '4.7-beta4-39287';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.