diff --git a/packages/ludic.render3d/terrain_ltt2_read.ludic b/packages/ludic.render3d/terrain_ltt2_read.ludic
index 131074ac..fbbc1a0e 100644
--- a/packages/ludic.render3d/terrain_ltt2_read.ludic
+++ b/packages/ludic.render3d/terrain_ltt2_read.ludic
@@ -124,9 +124,11 @@ function ltt2_gpu_coarse(render3d_st: mut Render3dState) -> void {
 @alloc_ok("a bake: once, at build time")
 export function terrain_tiles_bake(render3d_st: mut Render3dState, path: string, key: string, version: int, inputs_hash: long) -> bool {
   if render3d_st.ter_heights == null or render3d_st.ter_ortho_px == null or render3d_st.ter_normal_tex == 0 { return false }
+  Fs.mkdir(Path.dir(path))
   let f = file_open(path, "wb")
   if f == null { return false }
-  let base = 32 + (len(key) + 7) / 8 * 8
+  # the key and at least one zero after it, padded to 8: ludic.base's bake_write and baked_open
+  let base = 32 + (len(key) + 1 + 7) / 8 * 8
   let head = buffer(base)
   for i in 0 .. base { head[i] = 0 }
   file_write(f, data_of(head), base)