diff --git a/wp-includes/user.php b/wp-includes/user.php
index 65d24f65dc..a75d4832f4 100644
--- a/wp-includes/user.php
+++ b/wp-includes/user.php
@@ -664,6 +664,10 @@ function get_blogs_of_user( $id, $all = false ) {
 		return $blogs;
 	}
 
+	// Logged out users can't have blogs
+	if ( 0 === $id )
+		return false;
+
 	$blogs = wp_cache_get( 'blogs_of_user-' . $id, 'users' );
 
 	// Try priming the new cache from the old cache