diff --git a/src/structs.h b/src/structs.h
index 16a20716..6f95300 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -675,6 +675,7 @@
 {
     garray_T	al_ga;		/* growarray with the array of file names */
     int		al_refcount;	/* number of windows using this arglist */
+    int		id;		/* id of this arglist */
 } alist_T;
 
 /*