diff --git a/dlphelper/sorter.py b/dlphelper/sorter.py
index 7318738..681536f 100644
--- a/dlphelper/sorter.py
+++ b/dlphelper/sorter.py
@@ -439,7 +439,10 @@ def sort_plan(
             while p != Path("."):
                 if str(p) in prov:
                     dest_key, unit_name = str(p), prov[str(p)]
-                    inner_rel = rel.relative_to(p)
+                    # dirs-only relative path (the file name itself is
+                    # appended by build_target; keeping it here would
+                    # duplicate it in the target path)
+                    inner_rel = rel.relative_to(p).parent
                     break
                 p = p.parent
         if unit_name is None: