diff --git a/Lib/struct.py b/Lib/struct.py
index 027caa2..10085b7 100644
--- a/Lib/struct.py
+++ b/Lib/struct.py
@@ -36,7 +36,7 @@
 class Struct(_Struct):
     def __init__(self, fmt):
         if isinstance(fmt, str):
-            fmt = str8(fmt)
+            fmt = str8(fmt, 'latin1')
         _Struct.__init__(self, fmt)
 
 _MAXCACHE = 100