diff --git a/lib/specs/spec_0_1.js b/lib/specs/spec_0_1.js
index 3d87770..c7f5cc6 100644
--- a/lib/specs/spec_0_1.js
+++ b/lib/specs/spec_0_1.js
@@ -26,6 +26,10 @@ function Spec_0_1(_caller){
  */
 Spec_0_1.prototype.check = function() {
 
+  if(!this.payload['eventType']){
+    throw {message: "'eventType' is invalid"};
+  }
+
 }
 
 Spec_0_1.prototype.type = function(_type){
diff --git a/test/cloudevent_spec_0_1.js b/test/cloudevent_spec_0_1.js
index af391bf..aff92ea 100644
--- a/test/cloudevent_spec_0_1.js
+++ b/test/cloudevent_spec_0_1.js
@@ -1,8 +1,10 @@
 var expect       = require("chai").expect;
 var Cloudevent   = require("../index.js");
 
+const type = "com.github.pull.create";
+
 var cloudevent = new Cloudevent()
-                       .type("com.github.pull.create")
+                       .type(type)
                        .source("urn:event:from:myapi/resourse/123");
 
 describe("CloudEvents Spec 0.1 - JavaScript SDK", () => {
@@ -34,6 +36,20 @@ describe("CloudEvents Spec 0.1 - JavaScript SDK", () => {
       });
     });
 
+    describe("The Constraint check", () => {
+      describe("'eventType'", () => {
+        it("should throw an error when is an empty string", () => {
+          cloudevent.type("");
+          expect(cloudevent.format.bind(cloudevent)).to.throw("'eventType' is invalid");
+        });
+
+        it("should be a non-empty string", () => {
+          cloudevent.type(type);
+          cloudevent.format();
+        });
+      });
+    });
+
   });
 
 });