diff --git a/Lib/test/test_winreg.py b/Lib/test/test_winreg.py
index 3efe4663e8f..a9bc9621557 100644
--- a/Lib/test/test_winreg.py
+++ b/Lib/test/test_winreg.py
@@ -14,8 +14,8 @@ test_data = [
     ("StringExpand",  "The path is %path%",                    REG_EXPAND_SZ),
     ("Multi-string",  ["Lots", "of", "string", "values"],      REG_MULTI_SZ),
     ("Raw Data",      ("binary"+chr(0)+"data"),                REG_BINARY),
-    ("Big String",    "x"*(512*1024-4),                        REG_SZ),
-    ("Big Binary",    "x"*(1024*1024-4),                       REG_BINARY),
+    ("Big String",    "x"*(2**14-1),                           REG_SZ),
+    ("Big Binary",    "x"*(2**14),                             REG_BINARY),
 ]
 if have_unicode:
     test_data+=[