diff --git a/thunderbird.xml b/thunderbird.xml
index e6fe4924b000832bfca2ce4ec389a16c8c90a74d..ce9eb8452f795e7228f976daae3d67ff4611d49a 100755
--- a/thunderbird.xml
+++ b/thunderbird.xml
@@ -1,17 +1,18 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <packages>
 
-<package id="thunderbird" name="Mozilla Thunderbird" revision="%version%.3" reboot="false" priority="0">
+<package id="thunderbird" name="Mozilla Thunderbird" revision="%version%.1" reboot="false" priority="0">
 
 	<!-- NB: we've had problems with major version bumps which sometimes change the format of options
 			 we add in chemistry-prefs.js. Thus, we tie that to a version, and please test carefully when
        upgrading -->
 
- <variable name="version" value="31.4.0" />  
+ <variable name="version" value="31.5.0" />  
+ <variable name="prefsversion" value="31" />
  <check type="uninstall" condition="exists" path="Mozilla Thunderbird %version%.*" />
 
   <install cmd='"%software%\thunderbird\Thunderbird Setup %version%.exe" -ms' />
-  <install cmd='cmd /c copy "%software%\thunderbird\chemistry-prefs.js-%version%" "%programfileswpkg%\mozilla thunderbird\defaults\pref\chemistry-prefs.js" '/>
+  <install cmd='cmd /c copy "%software%\thunderbird\chemistry-prefs.js-%prefsversion%" "%programfileswpkg%\mozilla thunderbird\defaults\pref\chemistry-prefs.js" '/>
   <install cmd='cmd /c copy "%software%\thunderbird\cam.ac.uk.xml" "%programfileswpkg%\mozilla thunderbird\isp\cam.ac.uk.xml" '/>
   <install cmd='%software%\wpkg\tools\copydir.cmd "%software%\thunderbird\dictionaries" "%programfileswpkg%\mozilla thunderbird\dictionaries"' />
  
@@ -20,11 +21,10 @@
     <exit code="128" />
   </upgrade>
 
-  <!-- one-off commenting out for 31.4.0 revision 3: just copy updated prefs file -->
-  <!--  <upgrade cmd='"%software%\thunderbird\Thunderbird Setup %version%.exe" -ms' /> -->
-  <upgrade cmd='cmd /c copy "%software%\thunderbird\chemistry-prefs.js-%version%" "%programfileswpkg%\mozilla thunderbird\defaults\pref\chemistry-prefs.js" '/> 
-  <!--  <upgrade cmd='cmd /c copy "%software%\thunderbird\cam.ac.uk.xml" "%programfileswpkg%\mozilla thunderbird\isp\cam.ac.uk.xml" '/>
-  <upgrade cmd='%software%\wpkg\tools\copydir.cmd "%software%\thunderbird\dictionaries" "%programfileswpkg%\mozilla thunderbird\dictionaries"' /> -->
+  <upgrade cmd='"%software%\thunderbird\Thunderbird Setup %version%.exe" -ms' />
+  <upgrade cmd='cmd /c copy "%software%\thunderbird\chemistry-prefs.js-%prefsversion%" "%programfileswpkg%\mozilla thunderbird\defaults\pref\chemistry-prefs.js" '/> 
+  <upgrade cmd='cmd /c copy "%software%\thunderbird\cam.ac.uk.xml" "%programfileswpkg%\mozilla thunderbird\isp\cam.ac.uk.xml" '/>
+  <upgrade cmd='%software%\wpkg\tools\copydir.cmd "%software%\thunderbird\dictionaries" "%programfileswpkg%\mozilla thunderbird\dictionaries"' /> 
 
   <remove cmd='taskkill /F /IM thunderbird.exe'>
     <exit code="0" />