diff --git a/src/main/webapp/javascript/spotCompare.js b/src/main/webapp/javascript/spotCompare.js
index 2f89ff56f5..2a36681778 100755
--- a/src/main/webapp/javascript/spotCompare.js
+++ b/src/main/webapp/javascript/spotCompare.js
@@ -40,8 +40,10 @@ function overlaps(arr1, arr2) {
 }
 
 function hashDir(dir) {
-    if (dir.length != 36) return dir;
-    return dir.substr(0,1) + '/' + dir.substr(1,1) + '/' + dir;
+	if (typeof dir !== 'undefined') {
+    	if (dir.length != 36) return dir;
+    	return dir.substr(0,1) + '/' + dir.substr(1,1) + '/' + dir;
+	}
 }
 
 function spotDisplayInit(xml) {