diff --git a/src/HTTPCommands.cc b/src/HTTPCommands.cc
index 7e24305..d43a10c 100644
--- a/src/HTTPCommands.cc
+++ b/src/HTTPCommands.cc
@@ -705,6 +705,7 @@ bool HTTPRequest::Fail(const std::string &ecode, const std::string &emsg) {
 void HTTPRequest::Notify() {
 	std::lock_guard<std::mutex> lk(m_mtx);
 	m_result_ready = true;
+	modifyResponse(m_result);
 	m_cv.notify_one();
 }
 
diff --git a/src/HTTPCommands.hh b/src/HTTPCommands.hh
index 3e33f64..47a3d6a 100644
--- a/src/HTTPCommands.hh
+++ b/src/HTTPCommands.hh
@@ -162,6 +162,10 @@ class HTTPRequest {
 	// call to send more data.
 	bool Timeout() const { return m_timeout; }
 
+	// Function that can be overridden by test cases, allowing modification
+	// of the server response
+	virtual void modifyResponse(std::string &) {}
+
 	typedef std::map<std::string, std::string> AttributeValueMap;
 	AttributeValueMap query_parameters;
 	AttributeValueMap headers;
diff --git a/src/S3Commands.hh b/src/S3Commands.hh
index 1e9903d..1905ff1 100644
--- a/src/S3Commands.hh
+++ b/src/S3Commands.hh
@@ -217,7 +217,7 @@ class AmazonS3CompleteMultipartUpload : public AmazonRequest {
   protected:
 };
 
-class AmazonS3SendMultipartPart final : public AmazonRequest {
+class AmazonS3SendMultipartPart : public AmazonRequest {
 	using AmazonRequest::SendRequest;
 
   public:
diff --git a/test/s3_unit_tests.cc b/test/s3_unit_tests.cc
index 8fcf1cb..5cbc11f 100644
--- a/test/s3_unit_tests.cc
+++ b/test/s3_unit_tests.cc
@@ -112,6 +112,10 @@ s3.end
 	}
 
   public:
+	std::unique_ptr<S3FileSystem> GetFS() {
+		return std::unique_ptr<S3FileSystem>(new S3FileSystem(&m_log, m_configfn.c_str(), nullptr));
+	}
+
 	void WritePattern(const std::string &name, const off_t writeSize,
 					  const unsigned char chunkByte, const size_t chunkSize,
 					  bool known_size) {
@@ -260,6 +264,8 @@ s3.end
 		rv = fh->Close();
 		ASSERT_EQ(rv, 0);
 	}
+
+	XrdSysLogger m_log;
 };
 
 // Upload a single byte into S3
@@ -576,6 +582,49 @@ TEST_F(FileSystemS3Fixture, StressGet) {
 	}
 }
 
+class AmazonS3SendMultipartPartLowercase : public AmazonS3SendMultipartPart {
+protected:
+	virtual void modifyResponse(std::string &resp) override {
+		std::transform(resp.begin(), resp.end(), resp.begin(), [](unsigned char c){ return std::tolower(c); });
+	}
+};
+
+TEST_F(FileSystemS3Fixture, Etag) {
+	// Determine the S3 info.
+	auto oss = GetFS();
+	std::string exposedPath, object;
+	std::string path = "/test/etag_casesensitive_test";
+	ASSERT_EQ(oss->parsePath(path.c_str(), exposedPath, object), 0);
+
+	auto ai = oss->getS3AccessInfo(exposedPath, object);
+	ASSERT_NE(ai.get(), nullptr);
+	ASSERT_NE(ai->getS3BucketName(), "");
+	ASSERT_NE(object, "");
+
+	// Start an upload.
+	XrdSysLogger log;
+	XrdSysError err(&log, "test");
+	AmazonS3CreateMultipartUpload startUpload(*ai, object, err);
+	ASSERT_TRUE(startUpload.SendRequest());
+	std::string uploadId, errMsg;
+	startUpload.Results(uploadId, errMsg);
+
+	// Upload an etag.
+	AmazonS3SendMultipartPart upload_part_request(*ai, object, err);
+	std::string streaming_buffer = "aaaa";
+	ASSERT_TRUE(upload_part_request.SendRequest(streaming_buffer,
+										 std::to_string(1), uploadId,
+										 streaming_buffer.size(), true));
+	std::string etag;
+	ASSERT_TRUE(upload_part_request.GetEtag(etag));
+	std::vector<std::string> eTags;
+	eTags.push_back(etag);
+
+	// Finalize the object
+	AmazonS3CompleteMultipartUpload complete_upload_request(*ai, object, err);
+	ASSERT_TRUE(complete_upload_request.SendRequest(eTags, 2, uploadId));
+}
+
 int main(int argc, char **argv) {
 	::testing::InitGoogleTest(&argc, argv);
 	return RUN_ALL_TESTS();