diff --git a/src/uproot/writing/writable.py b/src/uproot/writing/writable.py
index e037cb8bc..22465a19f 100644
--- a/src/uproot/writing/writable.py
+++ b/src/uproot/writing/writable.py
@@ -37,6 +37,8 @@
 import uproot.models.TObjString
 import uproot.sink.file
 import uproot.writing._cascade
+import uproot.writing._cascadetree
+import uproot.writing.identify
 from uproot._util import no_filter, no_rename