diff --git a/lib/bindings/http/http_receiver.js b/lib/bindings/http/http_receiver.js
index 09128642..866c7966 100644
--- a/lib/bindings/http/http_receiver.js
+++ b/lib/bindings/http/http_receiver.js
@@ -2,7 +2,14 @@ const V03Binary = require("./receiver_binary_0_3");
 const V03Structured = require("./receiver_structured_0_3.js");
 const V1Binary = require("./receiver_binary_1.js");
 const V1Structured = require("./receiver_structured_1.js");
-const constants = require("./constants");
+const {
+  SPEC_V03,
+  SPEC_V1,
+  HEADER_CONTENT_TYPE,
+  MIME_CE,
+  BINARY_HEADERS_1,
+  DEFAULT_SPEC_VERSION_HEADER
+} = require("./constants");
 
 class HTTPReceiver {
   constructor() {
@@ -22,33 +29,37 @@ class HTTPReceiver {
     const mode = getMode(headers);
     const version = getVersion(mode, headers, body);
     switch (version) {
-      case constants.SPEC_V1:
+      case SPEC_V1:
         return this.receivers.v1[mode].parse(body, headers);
-      case constants.SPEC_V03:
+      case SPEC_V03:
         return this.receivers.v03[mode].parse(body, headers);
       default:
         console.error(
-          `Unknown spec version ${version}. Default to ${constants.SPEC_V1}`);
+          `Unknown spec version ${version}. Default to ${SPEC_V1}`);
         return this.receivers.v1[mode].parse(body, headers);
     }
   }
 }
 
 function getMode(headers) {
-  let mode = "binary";
-  const contentType = headers[constants.HEADER_CONTENT_TYPE];
-  if (contentType && contentType.startsWith(constants.MIME_CE)) {
+  let mode = "unknown";
+  const contentType = headers[HEADER_CONTENT_TYPE];
+  if (contentType && contentType.startsWith(MIME_CE)) {
     mode = "structured";
+  } else if (headers[BINARY_HEADERS_1.ID]) {
+    mode = "binary";
+  } else {
+    throw new TypeError("no cloud event detected");
   }
   return mode;
 }
 
 function getVersion(mode, headers, body) {
-  let version = constants.SPEC_V1; // default to 1.0
+  let version = SPEC_V1; // default to 1.0
 
   if (mode === "binary") {
     // Check the headers for the version
-    const versionHeader = headers[constants.DEFAULT_SPEC_VERSION_HEADER];
+    const versionHeader = headers[DEFAULT_SPEC_VERSION_HEADER];
     if (versionHeader) { version = versionHeader; }
   } else {
     // structured mode - the version is in the body
diff --git a/test/bindings/http/promiscuous_receiver_test.js b/test/bindings/http/promiscuous_receiver_test.js
index e99aa3cb..17ab81c7 100644
--- a/test/bindings/http/promiscuous_receiver_test.js
+++ b/test/bindings/http/promiscuous_receiver_test.js
@@ -18,6 +18,22 @@ const data = {
 };
 
 describe("HTTP Transport Binding Receiver for CloudEvents", () => {
+  describe("HTTP CloudEvent format detection", () => {
+    const specversion = "1.0";
+    it("Throws when the event format cannot be detected", () => {
+      const payload = {
+        id,
+        type,
+        source,
+        data,
+        specversion
+      };
+
+      expect(receiver.accept.bind(receiver, {}, payload))
+        .to.throw("no cloud event detected");
+    });
+  });
+
   describe("V1", () => {
     const specversion = "1.0";