diff --git a/Tools/msi/msi.py b/Tools/msi/msi.py
index ef36e36..e1f4371 100644
--- a/Tools/msi/msi.py
+++ b/Tools/msi/msi.py
@@ -118,7 +118,7 @@
 if micro:
     docfile = str(micro)
 if level < 0xf:
-    docfile = '%x%s' % (level, serial)
+    docfile += '%x%s' % (level, serial)
 docfile = 'python%s%s%s.chm' % (major, minor, docfile)
 
 # Build the mingw import library, libpythonXY.a