diff --git a/connection/connection.go b/connection/connection.go
index f141d255..8c05eeea 100644
--- a/connection/connection.go
+++ b/connection/connection.go
@@ -26,14 +26,20 @@ const (
 	MaxGracePeriod         = time.Minute * 3
 	MaxConcurrentStreams   = math.MaxUint32
 
-	contentTypeHeader = "content-type"
-	sseContentType    = "text/event-stream"
-	grpcContentType   = "application/grpc"
+	contentTypeHeader      = "content-type"
+	contentLengthHeader    = "content-length"
+	transferEncodingHeader = "transfer-encoding"
+
+	sseContentType     = "text/event-stream"
+	grpcContentType    = "application/grpc"
+	sseJsonContentType = "application/x-ndjson"
+
+	chunkTransferEncoding = "chunked"
 )
 
 var (
 	switchingProtocolText = fmt.Sprintf("%d %s", http.StatusSwitchingProtocols, http.StatusText(http.StatusSwitchingProtocols))
-	flushableContentTypes = []string{sseContentType, grpcContentType}
+	flushableContentTypes = []string{sseContentType, grpcContentType, sseJsonContentType}
 )
 
 // TunnelConnection represents the connection to the edge.
@@ -274,6 +280,22 @@ type ConnectedFuse interface {
 // Helper method to let the caller know what content-types should require a flush on every
 // write to a ResponseWriter.
 func shouldFlush(headers http.Header) bool {
+	// When doing Server Side Events (SSE), some frameworks don't respect the `Content-Type` header.
+	// Therefore, we need to rely on other ways to know whether we should flush on write or not. A good
+	// approach is to assume that responses without `Content-Length` or with `Transfer-Encoding: chunked`
+	// are streams, and therefore, should be flushed right away to the eyeball.
+	// References:
+	// - https://datatracker.ietf.org/doc/html/rfc7230#section-4.1
+	// - https://datatracker.ietf.org/doc/html/rfc9112#section-6.1
+	if contentLength := headers.Get(contentLengthHeader); contentLength == "" {
+		return true
+	}
+	if transferEncoding := headers.Get(transferEncodingHeader); transferEncoding != "" {
+		transferEncoding = strings.ToLower(transferEncoding)
+		if strings.Contains(transferEncoding, chunkTransferEncoding) {
+			return true
+		}
+	}
 	if contentType := headers.Get(contentTypeHeader); contentType != "" {
 		contentType = strings.ToLower(contentType)
 		for _, c := range flushableContentTypes {
@@ -282,7 +304,6 @@ func shouldFlush(headers http.Header) bool {
 			}
 		}
 	}
-
 	return false
 }
 
diff --git a/connection/connection_test.go b/connection/connection_test.go
index d1cb8557..a9dc5901 100644
--- a/connection/connection_test.go
+++ b/connection/connection_test.go
@@ -7,10 +7,12 @@ import (
 	"io"
 	"math/big"
 	"net/http"
+	"testing"
 	"time"
 
 	pkgerrors "github.com/pkg/errors"
 	"github.com/rs/zerolog"
+	"github.com/stretchr/testify/require"
 
 	cfdflow "github.com/cloudflare/cloudflared/flow"
 
@@ -209,3 +211,48 @@ func (mcf mockConnectedFuse) Connected() {}
 func (mcf mockConnectedFuse) IsConnected() bool {
 	return true
 }
+
+func TestShouldFlushHeaders(t *testing.T) {
+	tests := []struct {
+		headers     map[string]string
+		shouldFlush bool
+	}{
+		{
+			headers:     map[string]string{contentTypeHeader: "application/json", contentLengthHeader: "1"},
+			shouldFlush: false,
+		},
+		{
+			headers:     map[string]string{contentTypeHeader: "text/html", contentLengthHeader: "1"},
+			shouldFlush: false,
+		},
+		{
+			headers:     map[string]string{contentTypeHeader: "text/event-stream", contentLengthHeader: "1"},
+			shouldFlush: true,
+		},
+		{
+			headers:     map[string]string{contentTypeHeader: "application/grpc", contentLengthHeader: "1"},
+			shouldFlush: true,
+		},
+		{
+			headers:     map[string]string{contentTypeHeader: "application/x-ndjson", contentLengthHeader: "1"},
+			shouldFlush: true,
+		},
+		{
+			headers:     map[string]string{contentTypeHeader: "application/json"},
+			shouldFlush: true,
+		},
+		{
+			headers:     map[string]string{contentTypeHeader: "application/json", contentLengthHeader: "-1", transferEncodingHeader: "chunked"},
+			shouldFlush: true,
+		},
+	}
+
+	for _, test := range tests {
+		headers := http.Header{}
+		for k, v := range test.headers {
+			headers.Add(k, v)
+		}
+
+		require.Equal(t, test.shouldFlush, shouldFlush(headers))
+	}
+}