diff --git a/ChangeLog b/ChangeLog
index cb94fb876a..e5a3cf07f6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Aug 14 18:40:43 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ext/win32/lib/win32/registry.rb (API#SetValue): add terminator
+	  size, not 1 byte.  [ruby-core:70365] [Bug #11439]
+
 Thu Aug 13 22:49:42 2015  Juanito Fatas  <katehuang0320@gmail.com>
 
 	* lib/timeout.rb (Timeout#timeout): freeze a string message to
diff --git a/ext/win32/lib/win32/registry.rb b/ext/win32/lib/win32/registry.rb
index 1e12f4bafc..3830a5a3ee 100644
--- a/ext/win32/lib/win32/registry.rb
+++ b/ext/win32/lib/win32/registry.rb
@@ -326,7 +326,7 @@ For detail, see the MSDN[http://msdn.microsoft.com/library/en-us/sysinfo/base/pr
         case type
         when REG_SZ, REG_EXPAND_SZ, REG_MULTI_SZ
           data = data.encode(WCHAR)
-          size ||= data.size + 1
+          size ||= data.size + WCHAR_SIZE
         end
         check RegSetValueExW.call(hkey, make_wstr(name), 0, type, data, size)
       end