diff --git a/Lib/tarfile.py b/Lib/tarfile.py
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -178,7 +178,7 @@
             n = -(256 ** (len(s) - 1) - n)
     else:
         try:
-            n = int(nts(s, "ascii", "strict") or "0", 8)
+            n = int(nts(s, "ascii", "strict").rstrip() or "0", 8)
         except ValueError:
             raise InvalidHeaderError("invalid header")
     return n