1 files changed, 1 insertions, 1 deletions
diff --git a/Lib/difflib.py b/Lib/difflib.py
index 2095a5e..8296471 100644
--- a/Lib/difflib.py
+++ b/Lib/difflib.py
@@ -2079,7 +2079,7 @@ def restore(delta, which):
         tag = {1: "- ", 2: "+ "}[int(which)]
     except KeyError:
         raise ValueError('unknown delta choice (must be 1 or 2): %r'
-                           % which)
+                           % which) from None
     prefixes = ("  ", tag)
     for line in delta:
         if line[:2] in prefixes: