diff --git a/lib/index.js b/lib/index.js
index 25adbea94d0..0cd7c1a468f 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -440,15 +440,23 @@ Mongoose.prototype.modelNames.$hasSideEffects = true;
 /**
  * Generates a new Schema merged from others
  *
+ * @param {Object} [schema] Object with fields that the merged Schemas does not have
  * @param {Schema|Array} schemas
  * @param {Object} options options like in Schema constructor
- * @param {Boolean} control says when the generated schema will have control over merged schemas
+ * @param {Boolean} [control] says when the generated schema will have control over merged schemas
  * @api public
  * @return {Schema}
  */
-Mongoose.prototype.mergeSchemas = function(schemas, options, control)
-{
-  var schema = {}, dstSchema, dict = {};
+Mongoose.prototype.mergeSchemas = function(schema, schemas, options, control) {
+  if (schema.constructor !== Object) {
+    control = options;
+    options = schemas;
+    schemas = schema;
+    schema = undefined;
+  }
+  schema = schema || {};
+
+  var dstSchema, dict = {};
   var _kinds = [], _kind;
   var ret; // return object
 
@@ -468,14 +476,15 @@ Mongoose.prototype.mergeSchemas = function(schemas, options, control)
   schemas.forEach(function(obj) {
     if (!(obj instanceof Schema))
       throw new Error('Only Schema objects are allowed.');
+
     if (control && !obj.options.name)
       throw new Error('All SchemaS must have the name option defined.');
 
     _kinds.push(obj.options.name);
 
     obj.eachPath(function(p) {
-      // ignored fields
-      if (obj.options._id && p.path === obj.options.typeKey)
+      // ignored fields, for now (_id)
+      if (obj.options._id && p === '_id')
         return;
 
       p = obj.path(p);