diff --git a/lib/specs/spec_0_3.js b/lib/specs/spec_0_3.js
index 0a778b6..a0a80a8 100644
--- a/lib/specs/spec_0_3.js
+++ b/lib/specs/spec_0_3.js
@@ -3,7 +3,9 @@ const empty = require("is-empty");
 const Ajv   = require("ajv");
 
 const {
-  equalsOrThrow
+  equalsOrThrow,
+  isBase64,
+  clone
 } = require("../utils/fun.js");
 
 const RESERVED_ATTRIBUTES = {
@@ -19,8 +21,10 @@ const RESERVED_ATTRIBUTES = {
   data: "data"
 };
 
-const SUPPORTED_CONTENT_ENCODING = [];
-SUPPORTED_CONTENT_ENCODING.push("base64");
+const SUPPORTED_CONTENT_ENCODING = {};
+SUPPORTED_CONTENT_ENCODING["base64"] = {
+  check : (data) => isBase64(data)
+};
 
 const schema = require("../../ext/spec_0_3.json");
 
@@ -79,7 +83,9 @@ function Spec03(_caller){
 Spec03.prototype.check = function(ce){
   var toCheck = (!ce ? this.payload : ce);
 
-  var valid = isValidAgainstSchema(toCheck);
+  if(!isValidAgainstSchema(toCheck)) {
+    throw {message: "invalid payload", errors: isValidAgainstSchema.errors};
+  }
 
   Array.of(toCheck)
     .filter((tc) => (typeof tc.data) !== "string")
@@ -93,16 +99,31 @@ Spec03.prototype.check = function(ce){
   Array.of(toCheck)
     .filter((tc) => tc["datacontentencoding"])
     .map((tc) => tc["datacontentencoding"].toLocaleLowerCase("en-US"))
-    .filter((dce) => !SUPPORTED_CONTENT_ENCODING.includes(dce))
+    .filter((dce) => !Object.keys(SUPPORTED_CONTENT_ENCODING).includes(dce))
     .forEach((dce) => {
       throw {message: "invalid payload", errors: [
         "Unsupported content encoding: " + dce
       ]};
     });
 
-  if(!valid) {
-    throw {message: "invalid payload", errors: isValidAgainstSchema.errors};
-  }
+  Array.of(toCheck)
+    .filter((tc) => tc["datacontentencoding"])
+    .map((tc) => {
+      let newtc = clone(tc);
+      newtc.datacontentencoding =
+        newtc.datacontentencoding.toLocaleLowerCase("en-US");
+
+      return newtc;
+    })
+    .filter((tc) => Object.keys(SUPPORTED_CONTENT_ENCODING)
+                            .includes(tc.datacontentencoding))
+    .filter((tc) => !SUPPORTED_CONTENT_ENCODING[tc.datacontentencoding]
+                        .check(tc.data))
+    .forEach((tc) => {
+      throw {message: "invalid payload", errors: [
+        "Invalid content encoding of data: " + tc.data
+      ]};
+    });
 };
 
 Spec03.prototype.id = function(_id){
diff --git a/test/spec_0_3_tests.js b/test/spec_0_3_tests.js
index 2256f7a..70046f8 100644
--- a/test/spec_0_3_tests.js
+++ b/test/spec_0_3_tests.js
@@ -131,7 +131,7 @@ describe("CloudEvents Spec v0.3", () => {
           cloudevent.spec.payload.specversion = "0.3";
       });
 
-      it("should throw an erro when is empty", () => {
+      it("should throw an error when is empty", () => {
         cloudevent.spec.payload.specversion = "";
         expect(cloudevent.format.bind(cloudevent))
           .to
@@ -185,6 +185,22 @@ describe("CloudEvents Spec v0.3", () => {
         cloudevent.data(data);
       });
 
+      it("should throw an error when 'data' does not carry base64",
+        () => {
+
+        cloudevent
+          .data("no base 64 value")
+          .dataContentEncoding("base64")
+          .dataContentType("text/plain");
+
+        expect(cloudevent.format.bind(cloudevent))
+          .to
+          .throw("invalid payload");
+
+        delete cloudevent.spec.payload.datacontentencoding;
+        cloudevent.data(data);
+      });
+
       it("should accept when 'data' is a string", () => {
         cloudevent
           .data("Y2xvdWRldmVudHMK")