diff --git a/lib/model.js b/lib/model.js
index 9f12a0e..7f55934 100644
--- a/lib/model.js
+++ b/lib/model.js
@@ -20,7 +20,11 @@ var dateToJSON = function () { return { $$date: this.getTime() }; }
  */
 function checkKey (k, v) {
   if (k[0] === '$' && !(k === '$$date' && typeof v === 'number')) {
-    throw 'Keys cannot begin with the $ character';
+    throw 'Field names cannot begin with the $ character';
+  }
+
+  if (k.indexOf('.') !== -1) {
+    throw 'Field names cannot contain a .';
   }
 }
 
diff --git a/test/model.test.js b/test/model.test.js
index 42490f8..65c3991 100644
--- a/test/model.test.js
+++ b/test/model.test.js
@@ -148,6 +148,16 @@ describe('Model', function () {
       }).should.throw();
     });
 
+    it('Field names cannot contain a .', function () {
+      assert.isDefined(model.checkObject);
+
+      (function () {
+        model.checkObject({ "so.bad": true });
+      }).should.throw();
+
+      // Recursive behaviour testing done in the above test on $ signs
+    });
+
   });   // ==== End of 'Object checking' ==== //