diff --git a/db-config.php b/db-config.php
index 54f84310c8200de5156599466ecc63fe8100bd5f..c0cc8faeb7ff0d5d165352d070efc5ec9d50e419 100644
--- a/db-config.php
+++ b/db-config.php
@@ -14,4 +14,5 @@ include_once('r2db/db-backends.php');
 noblogs_load_global_dataset();
 
 // Add all the sharded blog databases.
+global $wpdb_reverse_backend_map;
 $wpdb_reverse_backend_map = noblogs_load_backends();