diff --git a/content/treestyletab/treestyletab.js b/content/treestyletab/treestyletab.js
index 0e54c339..5ea81e96 100644
--- a/content/treestyletab/treestyletab.js
+++ b/content/treestyletab/treestyletab.js
@@ -1117,7 +1117,12 @@ catch(e) {
 								if (!('TMP_contentAreaClick' in window) && // do nothing for Tab Mix Plus
 									TreeStyleTabService.checkToOpenChildTab()) {
 									TreeStyleTabService.stopToOpenChildTab();
-									urlSecurityCheck(href, 'nodePrincipal' in linkNode.ownerDocument ? linkNode.ownerDocument.nodePrincipal : linkNode.ownerDocument.location.href );
+									if (linkNode)
+										urlSecurityCheck(href,
+											'nodePrincipal' in linkNode.ownerDocument ?
+												linkNode.ownerDocument.nodePrincipal :
+												linkNode.ownerDocument.location.href
+										);
 									var postData = {};
 									href = getShortcutOrURI(href, postData);
 									if (!href) return false;