diff --git a/wp-includes/rest-api/class-wp-rest-request.php b/wp-includes/rest-api/class-wp-rest-request.php
index fdf13c46d1..4d4936b5f0 100644
--- a/wp-includes/rest-api/class-wp-rest-request.php
+++ b/wp-includes/rest-api/class-wp-rest-request.php
@@ -851,13 +851,13 @@ class WP_REST_Request implements ArrayAccess {
 				}
 
 				if ( is_wp_error( $valid_check ) ) {
-					$invalid_params[] = sprintf( '%s (%s)', $key, $valid_check->get_error_message() );
+					$invalid_params[ $key ] = $valid_check->get_error_message();
 				}
 			}
 		}
 
 		if ( $invalid_params ) {
-			return new WP_Error( 'rest_invalid_param', sprintf( __( 'Invalid parameter(s): %s' ), implode( ', ', $invalid_params ) ), array( 'status' => 400, 'params' => $invalid_params ) );
+			return new WP_Error( 'rest_invalid_param', sprintf( __( 'Invalid parameter(s): %s' ), implode( ', ', array_keys( $invalid_params ) ) ), array( 'status' => 400, 'params' => $invalid_params ) );
 		}
 
 		return true;
diff --git a/wp-includes/version.php b/wp-includes/version.php
index a47f0aaded..7964e5d1a9 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.5-alpha-35889';
+$wp_version = '4.5-alpha-35890';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.