diff --git a/module/repo/js/browse.ui.js b/module/repo/js/browse.ui.js
index d526dc3c94..12059b8f69 100644
--- a/module/repo/js/browse.ui.js
+++ b/module/repo/js/browse.ui.js
@@ -95,7 +95,9 @@ window.checkedChange = function(changes)
  */
 window.diffClick = function()
 {
-    var checkedIds  = getCurrentCheckedIds();
+    var checkedIds = getCurrentCheckedIds();
+    if(checkedIds.length < 2) return;
+
     var newDiffLink = diffLink.replace('{oldRevision}', revisionMap[checkedIds[1]]);
     newDiffLink     = newDiffLink.replace('{newRevision}', revisionMap[checkedIds[0]]);
 
diff --git a/module/repo/js/log.ui.js b/module/repo/js/log.ui.js
index 7c411cf9b3..3b971e80b2 100644
--- a/module/repo/js/log.ui.js
+++ b/module/repo/js/log.ui.js
@@ -74,7 +74,9 @@ function initRevisionMap(data)
  */
 window.diffClick = function()
 {
-    var checkedIds  = getCurrentCheckedIds();
+    var checkedIds = getCurrentCheckedIds();
+    if(checkedIds.length < 2) return;
+
     var newDiffLink = diffLink.replace('{oldRevision}', revisionMap[checkedIds[1]]);
     newDiffLink     = newDiffLink.replace('{newRevision}', revisionMap[checkedIds[0]]);
 
diff --git a/module/repo/ui/browse.html.php b/module/repo/ui/browse.html.php
index 724873da44..b61ed1ec14 100644
--- a/module/repo/ui/browse.html.php
+++ b/module/repo/ui/browse.html.php
@@ -236,7 +236,7 @@ $commentsTableData = initTableData($revisions, $config->repo->commentDtable->fie
 
 $readAllLink = $this->repo->createLink('log', "repoID=$repoID&objectID=$objectID&entry=" . $encodePath . "&revision=HEAD&type=$logType");
 
-$footToolbar['items'][] = array('text' => $lang->repo->diff, 'class' => "btn primary size-sm btn-diff", 'btnType' => 'primary', 'onClick' => jsRaw('window.diffClick'));
+$footToolbar['items'][] = array('text' => $lang->repo->diff, 'className' => "btn primary size-sm btn-diff", 'btnType' => 'primary', 'onClick' => jsRaw('window.diffClick'));
 $footToolbar['items'][] = array('text' => $lang->repo->allLog, 'url' => $readAllLink);
 
 sidebar
diff --git a/module/repo/ui/log.html.php b/module/repo/ui/log.html.php
index 1630b86802..d3929270d5 100644
--- a/module/repo/ui/log.html.php
+++ b/module/repo/ui/log.html.php
@@ -53,7 +53,7 @@ $config->repo->logDtable->fieldList['revision']['link'] = array('module' => 'rep
 
 $logs = initTableData($logs, $config->repo->logDtable->fieldList);
 
-$footToolbar['items'][] = array('text' => $lang->repo->diff, 'class' => "btn primary size-sm btn-diff", 'btnType' => 'primary', 'onClick' => jsRaw('window.diffClick'));
+$footToolbar['items'][] = array('text' => $lang->repo->diff, 'className' => "btn primary size-sm btn-diff", 'btnType' => 'primary', 'onClick' => jsRaw('window.diffClick'));
 
 featureBar(
     backBtn