diff --git a/wp-includes/canonical.php b/wp-includes/canonical.php
index 428e92ffcb..ae4cac572b 100644
--- a/wp-includes/canonical.php
+++ b/wp-includes/canonical.php
@@ -167,7 +167,7 @@ function redirect_canonical($requested_url=null, $do_redirect=true) {
 		} elseif ( is_single() && strpos($wp_rewrite->permalink_structure, '%category%') !== false ) {
 			$category = get_term_by('slug', get_query_var('category_name'), 'category');
 			$post_terms = wp_get_object_terms($wp_query->get_queried_object_id(), 'category');
-			if ( ! in_array($category, $post_terms) )
+			if ( (!$category || is_wp_error($category)) || ( !is_wp_error($post_terms) && !empty($post_terms) && !in_array($category, $post_terms) ) )
 				$redirect_url = get_permalink($wp_query->get_queried_object_id());
 		}