diff --git a/client.c b/client.c
index 612627bb4..ac186dadf 100644
--- a/client.c
+++ b/client.c
@@ -1644,6 +1644,7 @@ luaA_client_newindex(lua_State *L)
  * \param L The Lua VM state.
  * \return The number of elements pushed on stack.
  * \luastack
+ * \lfield id The window X id.
  * \lfield name The client title.
  * \lfield skip_taskbar True if the client does not want to be in taskbar.
  * \lfield type The window type (desktop, normal, dock, …).
@@ -1799,6 +1800,9 @@ luaA_client_index(lua_State *L)
             return 0;
         }
         break;
+      case A_TK_ID:
+        lua_pushnumber(L, (*c)->win);
+        break;
       case A_TK_LEADER_ID:
         lua_pushnumber(L, (*c)->leader_win);
         break;
diff --git a/common/tokenize.gperf b/common/tokenize.gperf
index bd843cdef..61fd96da4 100644
--- a/common/tokenize.gperf
+++ b/common/tokenize.gperf
@@ -44,6 +44,7 @@ hide
 honorsizehints
 icon
 icon_name
+id
 image
 instance
 key_press