diff --git a/indra/newview/build_win32_appConfig.py b/indra/newview/build_win32_appConfig.py
index 2ac0e17dc16d8f56046eb00d1301f2f575f39cf2..fb6a0258bcaad1ad0a286152cecea00f10ac95be 100644
--- a/indra/newview/build_win32_appConfig.py
+++ b/indra/newview/build_win32_appConfig.py
@@ -28,7 +28,7 @@
 # COMPLETENESS OR PERFORMANCE.
 # $/LicenseInfo$
 
-import sys, os
+import sys, os, re
 from xml.dom.minidom import parse
 
 def main():
@@ -43,7 +43,8 @@ def main():
     config_dom = parse(src_config_name)
     node = config_dom.getElementsByTagName('bindingRedirect')[0]
     node.setAttribute('newVersion', manifest_assm_ver)
-    node.setAttribute('oldVersion', node.getAttribute('oldVersion') + manifest_assm_ver)
+    src_old_ver = re.match('([^-]*-).*', node.getAttribute('oldVersion')).group(1)
+    node.setAttribute('oldVersion', src_old_ver + manifest_assm_ver)
     comment = config_dom.createComment("This file is automatically generated by the build. see indra/newview/build_win32_appConfig.py")
     config_dom.insertBefore(comment, config_dom.childNodes[0])