diff --git a/h2mux/header_test.go b/h2mux/header_test.go
index 95170230..787d278f 100644
--- a/h2mux/header_test.go
+++ b/h2mux/header_test.go
@@ -650,3 +650,27 @@ func randSeq(n int) string {
 	}
 	return string(b)
 }
+
+func BenchmarkH1ResponseToH2ResponseHeaders(b *testing.B) {
+	ser := "eC1mb3J3YXJkZWQtcHJvdG8:aHR0cHM;dXBncmFkZS1pbnNlY3VyZS1yZXF1ZXN0cw:MQ;YWNjZXB0LWxhbmd1YWdl:ZW4tVVMsZW47cT0wLjkscnU7cT0wLjg;YWNjZXB0LWVuY29kaW5n:Z3ppcA;eC1mb3J3YXJkZWQtZm9y:MTczLjI0NS42MC42;dXNlci1hZ2VudA:TW96aWxsYS81LjAgKE1hY2ludG9zaDsgSW50ZWwgTWFjIE9TIFggMTBfMTRfNikgQXBwbGVXZWJLaXQvNTM3LjM2IChLSFRNTCwgbGlrZSBHZWNrbykgQ2hyb21lLzg0LjAuNDE0Ny44OSBTYWZhcmkvNTM3LjM2;c2VjLWZldGNoLW1vZGU:bmF2aWdhdGU;Y2RuLWxvb3A:Y2xvdWRmbGFyZQ;c2VjLWZldGNoLWRlc3Q:ZG9jdW1lbnQ;c2VjLWZldGNoLXVzZXI:PzE;c2VjLWZldGNoLXNpdGU:bm9uZQ;Y29va2ll:X19jZmR1aWQ9ZGNkOWZjOGNjNWMxMzE0NTMyYTFkMjhlZDEyOWRhOTYwMTU2OTk1MTYzNDsgX19jZl9ibT1mYzY2MzMzYzAzZmM0MWFiZTZmOWEyYzI2ZDUwOTA0YzIxYzZhMTQ2LTE1OTU2MjIzNDEtMTgwMC1BZTVzS2pIU2NiWGVFM05mMUhrTlNQMG1tMHBLc2pQWkloVnM1Z2g1SkNHQkFhS1UxVDB2b003alBGN3FjMHVSR2NjZGcrWHdhL1EzbTJhQzdDVU4xZ2M9;YWNjZXB0:dGV4dC9odG1sLGFwcGxpY2F0aW9uL3hodG1sK3htbCxhcHBsaWNhdGlvbi94bWw7cT0wLjksaW1hZ2Uvd2VicCxpbWFnZS9hcG5nLCovKjtxPTAuOCxhcHBsaWNhdGlvbi9zaWduZWQtZXhjaGFuZ2U7dj1iMztxPTAuOQ"
+	h2, _ := DeserializeHeaders(ser)
+	h1 := make(http.Header)
+	for _, header := range h2 {
+		h1.Add(header.Name, header.Value)
+	}
+	h1.Add("Content-Length", "200")
+	h1.Add("Cf-Something", "Else")
+	h1.Add("Upgrade", "websocket")
+
+	h1resp := &http.Response{
+		StatusCode: 200,
+		Header: h1,
+	}
+
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_ = H1ResponseToH2ResponseHeaders(h1resp)
+	}
+}
+