diff --git a/devtools/shared/gcli/source/lib/gcli/commands/commands.js b/devtools/shared/gcli/source/lib/gcli/commands/commands.js
index 67793b2dc8f2..0af4be620a9b 100644
--- a/devtools/shared/gcli/source/lib/gcli/commands/commands.js
+++ b/devtools/shared/gcli/source/lib/gcli/commands/commands.js
@@ -335,10 +335,10 @@ Parameter.prototype.toJson = function() {
   };
 
   // Values do not need to be serializable, so we don't try. For the client
-  // side (which doesn't do any executing) we don't actually care what the
-  // default value is, just that it exists
+  // side (which doesn't do any executing) we only care whether default value is
+  // undefined, null, or something else.
   if (this.paramSpec.defaultValue !== undefined) {
-    json.defaultValue = {};
+    json.defaultValue = (this.paramSpec.defaultValue === null) ? null : {};
   }
   if (this.paramSpec.description != null) {
     json.description = this.paramSpec.description;
diff --git a/devtools/shared/gcli/source/lib/gcli/commands/help.js b/devtools/shared/gcli/source/lib/gcli/commands/help.js
index 317f80240c75..7d1cc9087716 100644
--- a/devtools/shared/gcli/source/lib/gcli/commands/help.js
+++ b/devtools/shared/gcli/source/lib/gcli/commands/help.js
@@ -69,7 +69,7 @@ function getHelpManData(commandData, context) {
       }
       else {
         // We need defaultText to work the text version of defaultValue
-        input = l10n.lookupFormat('helpManOptional');
+        input = l10n.lookup('helpManOptional');
         /*
         var val = param.type.stringify(param.defaultValue);
         input = Promise.resolve(val).then(function(defaultValue) {