diff --git a/kmod/src/btree.c b/kmod/src/btree.c
index 23878451..4cfe1feb 100644
--- a/kmod/src/btree.c
+++ b/kmod/src/btree.c
@@ -414,9 +414,9 @@ static struct scoutfs_block *try_split(struct super_block *sb,
 
 	/* only grow the tree once we have the split neighbour */
 	if (par_bl) {
-		struct scoutfs_key ones;
-		memset(&ones, 0xff, sizeof(ones));
-		create_parent_item(parent, right, &ones);
+		struct scoutfs_key maximal;
+		scoutfs_set_max_key(&maximal);
+		create_parent_item(parent, right, &maximal);
 	}
 
 	move_items(left, right, false, used_total(right) / 2);
diff --git a/kmod/src/key.h b/kmod/src/key.h
index b61967d0..11a7c721 100644
--- a/kmod/src/key.h
+++ b/kmod/src/key.h
@@ -62,6 +62,11 @@ static inline void scoutfs_set_key(struct scoutfs_key *key, u64 inode, u8 type,
 	key->offset = cpu_to_le64(offset);
 }
 
+static inline void scoutfs_set_max_key(struct scoutfs_key *key)
+{
+	scoutfs_set_key(key, ~0ULL, ~0, ~0ULL);
+}
+
 static inline void scoutfs_inc_key(struct scoutfs_key *key)
 {
 	le64_add_cpu(&key->offset, 1);