diff --git a/transmission/transmission.go b/transmission/transmission.go
index 08a8203..e44fe74 100644
--- a/transmission/transmission.go
+++ b/transmission/transmission.go
@@ -388,6 +388,7 @@ func (b *batchAgg) fireBatch(events []*Event) {
 		var req *http.Request
 		reqBody, zipped := buildReqReader(encEvs, !b.disableCompression)
 		req, err = http.NewRequest("POST", url.String(), reqBody)
+		req.ContentLength = int64(reqBody.Len())
 		req.Header.Set("Content-Type", contentType)
 		if zipped {
 			req.Header.Set("Content-Encoding", "zstd")
@@ -630,14 +631,29 @@ func (b *batchAgg) enqueueErrResponses(err error, events []*Event, duration time
 
 var zstdBufferPool sync.Pool
 
+type ReqReader interface {
+	io.ReadCloser
+	Len() int
+}
+
 type pooledReader struct {
-	*bytes.Reader
+	bytes.Reader
 	buf []byte
 }
 
+type SimpleReader struct {
+	bytes.Reader
+}
+
+func (r SimpleReader) Close() error {
+	return nil
+}
+
 func (r *pooledReader) Close() error {
+	// Ensure further attempts to read will return io.EOF
+	r.Reset(nil)
+	// Then reset and give up ownership of the buffer.
 	zstdBufferPool.Put(r.buf[:0])
-	r.Reader = nil
 	r.buf = nil
 	return nil
 }
@@ -661,9 +677,9 @@ func init() {
 	}
 }
 
-// buildReqReader returns an io.Reader and a boolean, indicating whether or not
-// the io.Reader is compressed.
-func buildReqReader(jsonEncoded []byte, compress bool) (io.ReadCloser, bool) {
+// buildReqReader returns an io.ReadCloser and a boolean, indicating whether or not
+// the underlying bytes.Reader is compressed.
+func buildReqReader(jsonEncoded []byte, compress bool) (ReqReader, bool) {
 	if compress {
 		var buf []byte
 		if found, ok := zstdBufferPool.Get().([]byte); ok {
@@ -671,12 +687,15 @@ func buildReqReader(jsonEncoded []byte, compress bool) (io.ReadCloser, bool) {
 		}
 
 		buf = zstdEncoder.EncodeAll(jsonEncoded, buf)
-		return &pooledReader{
-			Reader: bytes.NewReader(buf),
-			buf:    buf,
-		}, true
+		reader := pooledReader{
+			buf: buf,
+		}
+		reader.Reset(reader.buf)
+		return &reader, true
 	}
-	return ioutil.NopCloser(bytes.NewReader(jsonEncoded)), false
+	var reader SimpleReader
+	reader.Reset(jsonEncoded)
+	return &reader, false
 }
 
 // nower to make testing easier
diff --git a/transmission/transmission_test.go b/transmission/transmission_test.go
index 6579063..a8f9b31 100644
--- a/transmission/transmission_test.go
+++ b/transmission/transmission_test.go
@@ -124,7 +124,13 @@ type FakeRoundTripper struct {
 
 func (f *FakeRoundTripper) RoundTrip(r *http.Request) (*http.Response, error) {
 	f.req = r
+	if r.ContentLength == 0 {
+		panic("Expected a content length for all POST payloads.")
+	}
 	bodyBytes, _ := ioutil.ReadAll(r.Body)
+	if r.ContentLength != int64(len(bodyBytes)) {
+		panic("Content length did not match number of read bytes.")
+	}
 	f.reqBody = string(bodyBytes)
 
 	// Honeycomb servers response to msgpack requests with msgpack responses,
@@ -486,7 +492,13 @@ func (f *FancyFakeRoundTripper) RoundTrip(r *http.Request) (*http.Response, erro
 		headerKeys := strings.Split(reqHeader, ",")
 		expectedURL, _ := url.Parse(fmt.Sprintf("%s/1/batch/%s", headerKeys[0], headerKeys[2]))
 		if r.Header.Get("X-Honeycomb-Team") == headerKeys[1] && r.URL.String() == expectedURL.String() {
+			if r.ContentLength == 0 {
+				panic("Expected a content length for all POST payloads.")
+			}
 			bodyBytes, _ := ioutil.ReadAll(r.Body)
+			if r.ContentLength != int64(len(bodyBytes)) {
+				panic("Content length did not match number of read bytes.")
+			}
 			f.reqBody = string(bodyBytes)
 
 			// make sure body is legitimately compressed json
@@ -1085,7 +1097,7 @@ func TestHoneycombSenderAddingResponsesBlocking(t *testing.T) {
 
 }
 
-func TestBuildReqReaderNoGzip(t *testing.T) {
+func TestBuildReqReaderCompress(t *testing.T) {
 	payload := []byte(`{"hello": "world"}`)
 
 	// Ensure that if compress is false, we get expected values
@@ -1095,7 +1107,7 @@ func TestBuildReqReaderNoGzip(t *testing.T) {
 	testOK(t, err)
 	testEquals(t, readBuffer, payload)
 
-	// Ensure that if useGzip is true, we get compressed values
+	// Ensure that if compress is true, we get compressed values
 	reader, compressed = buildReqReader([]byte(`{"hello": "world"}`), true)
 	testEquals(t, compressed, true)
 	readBuffer, err = ioutil.ReadAll(reader)
@@ -1104,6 +1116,14 @@ func TestBuildReqReaderNoGzip(t *testing.T) {
 	decompressed, err := zstd.Decompress(nil, readBuffer)
 	testOK(t, err)
 	testEquals(t, decompressed, payload)
+
+	// Ensure that calling Close() on the compressed buffer, then
+	// attempting to Read() returns io.EOF but no crash.
+	// Needed to support https://go-review.googlesource.com/c/net/+/355491
+	reader, _ = buildReqReader([]byte(`{"hello": "world"}`), true)
+	reader.Close()
+	_, err = reader.Read(nil)
+	testEquals(t, err, io.EOF)
 }
 
 func TestMsgpackArrayEncoding(t *testing.T) {