diff --git a/wp-includes/plugin.php b/wp-includes/plugin.php
index 1168f079e0..343bdceb7c 100644
--- a/wp-includes/plugin.php
+++ b/wp-includes/plugin.php
@@ -785,6 +785,6 @@ function _wp_filter_build_unique_id($tag, $function, $priority) {
 		}
 	} else if ( is_string($function[0]) ) {
 		// Static Calling
-		return $function[0].$function[1];
+		return $function[0] . '::' . $function[1];
 	}
 }