diff --git a/kmod/src/btree.c b/kmod/src/btree.c
index db857103..ab2387bb 100644
--- a/kmod/src/btree.c
+++ b/kmod/src/btree.c
@@ -151,6 +151,8 @@ static int copy_to_val(struct scoutfs_btree_val *val,
 	/* XXX corruption */
 	if (val->check_size_eq && val_len != scoutfs_btree_val_length(val))
 		return -EIO;
+	if (val->check_size_lte && val_len > scoutfs_btree_val_length(val))
+		return -EOVERFLOW;
 
 	for (i = 0, off = 0; val_len > 0 && i < ARRAY_SIZE(val->vec); i++) {
 		kv = &val->vec[i];
diff --git a/kmod/src/btree.h b/kmod/src/btree.h
index 7615a733..6df548d1 100644
--- a/kmod/src/btree.h
+++ b/kmod/src/btree.h
@@ -6,6 +6,7 @@
 struct scoutfs_btree_val {
 	struct kvec vec[3];
 	unsigned int check_size_eq:1;
+	unsigned int check_size_lte:1;
 };
 
 static inline void __scoutfs_btree_init_val(struct scoutfs_btree_val *val,