diff --git a/http_proxy.go b/http_proxy.go
index 41b8392a..687d9860 100644
--- a/http_proxy.go
+++ b/http_proxy.go
@@ -100,7 +100,7 @@ func (c *HTTPProxyConfig) Validate() error {
 	if err := c.HTTPServerConfig.Validate(); err != nil {
 		return err
 	}
-	if c.Protocol != HTTPScheme && c.Protocol != HTTPSScheme && c.Protocol != TunnelScheme {
+	if c.Protocol != HTTPScheme && c.Protocol != HTTPSScheme {
 		return fmt.Errorf("unsupported protocol: %s", c.Protocol)
 	}
 	if !c.ProxyLocalhost.isValid() {
diff --git a/http_server.go b/http_server.go
index 9dbd49cc..141cbf50 100644
--- a/http_server.go
+++ b/http_server.go
@@ -27,10 +27,9 @@ import (
 type Scheme string
 
 const (
-	HTTPScheme   Scheme = "http"
-	HTTPSScheme  Scheme = "https"
-	HTTP2Scheme  Scheme = "h2"
-	TunnelScheme Scheme = "tunnel"
+	HTTPScheme  Scheme = "http"
+	HTTPSScheme Scheme = "https"
+	HTTP2Scheme Scheme = "h2"
 )
 
 func (s Scheme) String() string {