diff --git a/defaults/preferences/treestyletab.js b/defaults/preferences/treestyletab.js
index b655353a..a549ebea 100644
--- a/defaults/preferences/treestyletab.js
+++ b/defaults/preferences/treestyletab.js
@@ -54,7 +54,7 @@ pref("extensions.treestyletab.autoExpand.delay",       500);
 pref("extensions.treestyletab.autoExpand.intelligently", true);
 pref("extensions.treestyletab.autoExpand.collapseFinally", false);
 pref("extensions.treestyletab.maxTreeLevel.horizontal", 0);
-pref("extensions.treestyletab.maxTreeLevel.vertical",   -1);
+pref("extensions.treestyletab.maxTreeLevel.vertical",   999);
 pref("extensions.treestyletab.maxTreeLevel.phisical", false);
 pref("extensions.treestyletab.indent",          12);
 pref("extensions.treestyletab.indent.property", "margin");