diff --git a/packages/kopano-ol-extension-nightly/kopano-ol-extension-nightly.nuspec b/packages/kopano-ol-extension-nightly/kopano-ol-extension-nightly.nuspec
index 8765a45..c60d743 100755
--- a/packages/kopano-ol-extension-nightly/kopano-ol-extension-nightly.nuspec
+++ b/packages/kopano-ol-extension-nightly/kopano-ol-extension-nightly.nuspec
@@ -2,7 +2,7 @@
 <package xmlns="http://schemas.microsoft.com/packaging/2011/08/nuspec.xsd">
     <metadata>
         <id>kopano-ol-extension-nightly</id>
-        <version>1.6.246</version>
+        <version>1.6.255</version>
         <title>Kopano Outlook Extension</title>
         <authors>Kopano</authors>
         <owners>foo.li systeme + software</owners>
@@ -12,7 +12,7 @@
         <requireLicenseAcceptance>true</requireLicenseAcceptance>
         <description>Kopano Outlook Extension (nightly)</description>
         <summary>Kopano OL Extension Nightly (unsupported)</summary>
-        <releaseNotes>upgrade to 1.6.246 (08-11-2017)</releaseNotes>
+        <releaseNotes>upgrade to 1.6.255 (07-12-2017)</releaseNotes>
         <copyright>2017 Kopano</copyright>
         <language />
         <tags>groupware kopano outlook-extension nightly</tags>
diff --git a/packages/kopano-ol-extension-nightly/tools/chocolateyinstall.ps1 b/packages/kopano-ol-extension-nightly/tools/chocolateyinstall.ps1
index 0df2bee..71f5fc0 100755
--- a/packages/kopano-ol-extension-nightly/tools/chocolateyinstall.ps1
+++ b/packages/kopano-ol-extension-nightly/tools/chocolateyinstall.ps1
@@ -6,13 +6,13 @@ $packageName    = 'kopano-ol-extension-nightly'
 $packageSearch  = 'Kopano OL Extension'
 $installerType  = 'msi'
 $silentArgs     = '/qb'
-$version        = '1.6.246'
-$intvers        = '1.6-246'
+$version        = '1.6.255'
+$intvers        = '1.6-255'
 $url            = 'https://download.kopano.io/community/olextension:/KopanoOLExtension-' + $intvers + '-32bit.msi'
 $url64          = 'https://download.kopano.io/community/olextension:/KopanoOLExtension-' + $intvers + '-64bit.msi'
-$checksum       = '6F877FB2C693681F5E2002C5F9B365372A034C77'
+$checksum       = '6f970ab5a5f26e786379426be8392a8b43c406ed'
 $checksumType   = 'sha1'
-$checksum64     = '1CA137E458ADEB7241F33CBD82E42E44925A109A'
+$checksum64     = 'e311da9c922c6af5ebf9763b94788499ee66e7e9'
 $checksumType64 = $checksumType
 
 try {