diff --git a/samples/memfs/memfs.go b/samples/memfs/memfs.go
index 0d50297..a09e79f 100644
--- a/samples/memfs/memfs.go
+++ b/samples/memfs/memfs.go
@@ -857,6 +857,6 @@ func (fs *memFS) Fallocate(ctx context.Context,
 	fs.mu.Lock()
 	defer fs.mu.Unlock()
 	inode := fs.getInodeOrDie(op.Inode)
-	inode.Fallocate(op.Mode, op.Length, op.Length)
+	inode.Fallocate(op.Mode, op.Offset, op.Length)
 	return nil
 }