diff --git a/src/structs.h b/src/structs.h
index 4a0c10a..68a9ba9 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1250,6 +1250,7 @@
 				// array is "ht_mask" + 1)
     long_u	ht_used;	// number of items used
     long_u	ht_filled;	// number of items used + removed
+    int		ht_changed;	// incremented when adding or removing an item
     int		ht_locked;	// counter for hash_lock()
     int		ht_error;	// when set growing failed, can't add more
 				// items before growing works