diff --git a/layout/tools/reftest/reftest.js b/layout/tools/reftest/reftest.js
index 0272c4289ae..b7d0f57beee 100644
--- a/layout/tools/reftest/reftest.js
+++ b/layout/tools/reftest/reftest.js
@@ -365,6 +365,9 @@ function BuildConditionSandbox(aURL) {
       getIntPref:  function(p) { return this._prefs.getIntPref(p); }
     }
 
+    dump("REFTEST INFO | Dumping JSON representation of sandbox \n");
+    dump("REFTEST INFO | " + JSON.stringify(sandbox) + " \n");
+
     return sandbox;
 }