--- a/playground/jsonld.js	Mon Apr 16 15:03:06 2012 -0400
+++ b/playground/jsonld.js	Mon Apr 16 16:15:05 2012 -0400
@@ -763,7 +763,7 @@
   }
 
   // return null for invalid key
-  if(!key) {
+  if(key === null) {
     rval = null;
   }
   // return entire context entry if type is unspecified