diff --git a/types/memcached/index.d.ts b/types/memcached/index.d.ts
index fffbb57c82..8e330fa88d 100644
--- a/types/memcached/index.d.ts
+++ b/types/memcached/index.d.ts
@@ -280,5 +280,9 @@ declare namespace Memcached {
          * 5000, the idle timeout for the connections.
          */
         idle ?: number;
+        /**
+         * '', sentinel to prepend to all memcache keys for namespacing the entries.
+         */
+        namespace ?: string;
     }
 }