diff --git a/src/structs.h b/src/structs.h
index a53a125..23ce826 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1916,7 +1916,9 @@
 
     int		b_changed;	/* 'modified': Set to TRUE if something in the
 				   file has been changed and not written out. */
-    int		b_changedtick;	/* incremented for each change, also for undo */
+    varnumber_T	*b_changedtick;	/* points into b:changedtick or b_ct_val;
+				   incremented for each change, also for undo */
+    varnumber_T b_ct_val;	/* fallback for b:changedtick */
 
     int		b_saving;	/* Set to TRUE if we are in the middle of
 				   saving the buffer. */