diff --git a/router-tests/events/kafka_events_test.go b/router-tests/events/kafka_events_test.go
index 8e6a7ec52b..9916bfb256 100644
--- a/router-tests/events/kafka_events_test.go
+++ b/router-tests/events/kafka_events_test.go
@@ -422,6 +422,7 @@ func TestKafkaEvents(t *testing.T) {
 		}
 
 		assertMultipartPrefix := func(t *testing.T, reader *bufio.Reader) {
+			assertLineEquals(t, reader, "")
 			assertLineEquals(t, reader, "--graphql")
 			assertLineEquals(t, reader, "Content-Type: application/json")
 			assertLineEquals(t, reader, "")
diff --git a/router-tests/events/nats_events_test.go b/router-tests/events/nats_events_test.go
index b273e9bccc..e07cd63196 100644
--- a/router-tests/events/nats_events_test.go
+++ b/router-tests/events/nats_events_test.go
@@ -285,6 +285,7 @@ func TestNatsEvents(t *testing.T) {
 		}
 
 		assertMultipartPrefix := func(t *testing.T, reader *bufio.Reader) {
+			assertLineEquals(t, reader, "")
 			assertLineEquals(t, reader, "--graphql")
 			assertLineEquals(t, reader, "Content-Type: application/json")
 			assertLineEquals(t, reader, "")
@@ -322,7 +323,7 @@ func TestNatsEvents(t *testing.T) {
 					require.Equal(t, http.StatusOK, resp.StatusCode)
 					defer resp.Body.Close()
 
-					require.Equal(t, "application/json", resp.Header.Get("Content-Type"))
+					require.Equal(t, "multipart/mixed; boundary=graphql", resp.Header.Get("Content-Type"))
 					require.Equal(t, "no-cache", resp.Header.Get("Cache-Control"))
 					require.Equal(t, "no", resp.Header.Get("X-Accel-Buffering"))
 
diff --git a/router/core/flushwriter.go b/router/core/flushwriter.go
index 95ca14fb92..b0a5d7f595 100644
--- a/router/core/flushwriter.go
+++ b/router/core/flushwriter.go
@@ -20,6 +20,7 @@ const (
 	jsonContent          = "application/json"
 	sseMimeType          = "text/event-stream"
 	heartbeat            = "{}"
+	multipartContent     = multipartMime + "; boundary=" + multipartBoundary
 )
 
 type HttpFlushWriter struct {
@@ -165,7 +166,7 @@ func setSubscriptionHeaders(wgParams SubscriptionParams, r *http.Request, w http
 	}
 
 	if wgParams.UseMultipart {
-		w.Header().Set("Content-Type", jsonContent)
+		w.Header().Set("Content-Type", multipartContent)
 		if r.ProtoMajor == 1 {
 			w.Header().Set("Transfer-Encoding", "chunked")
 		}
@@ -206,7 +207,7 @@ func GetWriterPrefix(sse bool, multipart bool) string {
 	if sse {
 		flushBreak = "event: next\ndata: "
 	} else if multipart {
-		flushBreak = "--" + multipartBoundary + "\nContent-Type: " + jsonContent + "\n\n"
+		flushBreak = "\r\n--" + multipartBoundary + "\nContent-Type: " + jsonContent + "\r\n\r\n"
 	}
 
 	return flushBreak