diff --git a/src/message/http/index.ts b/src/message/http/index.ts
index ad9fd701..71a6642f 100644
--- a/src/message/http/index.ts
+++ b/src/message/http/index.ts
@@ -181,8 +181,10 @@ function parseBinary<T>(message: Message, version: string): CloudEvent<T> {
   }
 
   // Every unprocessed header can be an extension
+  // Header names are case-insensitive, so match the prefix and known attributes in any case
   for (const header in headers) {
-    if (header.startsWith(CONSTANTS.EXTENSIONS_PREFIX)) {
+    const lowerCaseHeader = header.toLowerCase();
+    if (lowerCaseHeader.startsWith(CONSTANTS.EXTENSIONS_PREFIX) && !parserMap[lowerCaseHeader]) {
       eventObj[header.substring(CONSTANTS.EXTENSIONS_PREFIX.length)] = headers[header];
     }
   }
diff --git a/test/integration/message_test.ts b/test/integration/message_test.ts
index 9ddb292d..10f275d1 100644
--- a/test/integration/message_test.ts
+++ b/test/integration/message_test.ts
@@ -166,6 +166,27 @@ describe("HTTP transport", () => {
     }).to.throw("invalid attribute name: \"LUNCH\"");
   });
 
+  it("Includes extensions in binary mode when the header prefix is not lower case", () => {
+    const message = {
+      body: `{ "greeting": "hello" }`,
+      headers: {
+        "Ce-Id": "1234",
+        "Ce-Source": "test",
+        "Ce-Type": "test.event",
+        "Ce-Specversion": V1,
+        "Ce-myext": "val",
+        "CE-otherext": "other",
+      },
+    };
+    const event = HTTP.toEvent(message) as CloudEvent;
+    expect(event.myext).to.equal("val");
+    expect(event.otherext).to.equal("other");
+    expect(event.id).to.equal("1234");
+    expect(event).not.to.have.property("Id");
+    expect(event).not.to.have.property("Specversion");
+    expect(() => event.validate()).not.to.throw();
+  });
+
   it("Can detect CloudEvent binary Messages with weird versions", () => {
     // Now create a message that is an event
     const message = {