diff --git a/wp-includes/class-wp.php b/wp-includes/class-wp.php
index 56a5561f13..e7191b6161 100644
--- a/wp-includes/class-wp.php
+++ b/wp-includes/class-wp.php
@@ -468,7 +468,7 @@ class WP {
 			$GLOBALS['single'] = 1;
 		}
 
-		if ( $wp_query->is_author() && $wp_query->post )
+		if ( $wp_query->is_author() && isset( $wp_query->post ) )
 			$GLOBALS['authordata'] = get_userdata( $wp_query->post->post_author );
 	}