diff --git a/src/main/php/admin/update/update.php b/src/main/php/admin/update/update.php
index 0c8bf745..d54bb9cd 100644
--- a/src/main/php/admin/update/update.php
+++ b/src/main/php/admin/update/update.php
@@ -484,16 +484,11 @@ function run($installedVersion) {
         }
 
         if(version_compare ( '6.0.101', $installedVersion ) > 0) {
-            file_put_contents(MC_ROOT_PATH . 'conf/system.conf.php', 'DEFINE("ENABLE_VIEWER_JS", true); # toggle viewer.js for office documents', FILE_APPEND | LOCK_EX);
+            file_put_contents(MC_ROOT_PATH . 'conf/system.conf.php', 'DEFINE("ENABLE_VIEWER_JS", true); # toggle viewer.js for office documents' . PHP_EOL, FILE_APPEND | LOCK_EX);
         }
 
         if(version_compare ( '6.0.102', $installedVersion ) > 0) {
-            $viewer_js_conf = "VIEWER_JS_CONFIG = [
-                'pdf',
-                //'office',
-                //'spreadsheet'
-            ];";
-            file_put_contents(MC_ROOT_PATH . 'conf/system.conf.php', $viewer_js_conf, FILE_APPEND | LOCK_EX);
+            file_put_contents(MC_ROOT_PATH . 'conf/system.conf.php', '$VIEWER_JS_CONFIG = ["pdf"]; # office and spreadsheet also available' . PHP_EOL, FILE_APPEND | LOCK_EX);
         }
 
 
diff --git a/src/main/php/install/_tmpl/conf/system.conf.php b/src/main/php/install/_tmpl/conf/system.conf.php
index 67a1d5f1..c52314a2 100644
--- a/src/main/php/install/_tmpl/conf/system.conf.php
+++ b/src/main/php/install/_tmpl/conf/system.conf.php
@@ -14,6 +14,7 @@
 $DATAPROTECTIONREGULATION_CONFIG = ["enabled" => false, "modules" => [], "urls" => ['/.*/' => ["name" => "Example", "url" => "http://example"]]];
 
 DEFINE("ENABLE_VIEWER_JS", true); # toggle viewer.js for office documents
+$VIEWER_JS_CONFIG = ["pdf"]; # office and spreadsheet also available
 
 $ESRENDER_SESSION_NAME = 'ESSID';