diff --git a/lib/python/pyflyby/_importdb.py b/lib/python/pyflyby/_importdb.py
index 0fa72fa0..4df4186e 100644
--- a/lib/python/pyflyby/_importdb.py
+++ b/lib/python/pyflyby/_importdb.py
@@ -28,7 +28,7 @@
 else:
     from typing import Self
 
-SUPPORT_DEPRECATED_BEHAVIOR = True
+SUPPORT_DEPRECATED_BEHAVIOR = False
 
 @memoize
 def _find_etc_dirs():