diff --git a/src/net/http/cgi/host.go b/src/net/http/cgi/host.go
index 0d43e140d56..349dda15acf 100644
--- a/src/net/http/cgi/host.go
+++ b/src/net/http/cgi/host.go
@@ -138,7 +138,6 @@ func (h *Handler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 
 	env := []string{
 		"SERVER_SOFTWARE=go",
-		"SERVER_NAME=" + req.Host,
 		"SERVER_PROTOCOL=HTTP/1.1",
 		"HTTP_HOST=" + req.Host,
 		"GATEWAY_INTERFACE=CGI/1.1",
@@ -158,6 +157,12 @@ func (h *Handler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 		env = append(env, "REMOTE_ADDR="+req.RemoteAddr, "REMOTE_HOST="+req.RemoteAddr)
 	}
 
+	if hostDomain, _, err := net.SplitHostPort(req.Host); err == nil {
+		env = append(env, "SERVER_NAME="+hostDomain)
+	} else {
+		env = append(env, "SERVER_NAME="+req.Host)
+	}
+
 	if req.TLS != nil {
 		env = append(env, "HTTPS=on")
 	}
diff --git a/src/net/http/cgi/host_test.go b/src/net/http/cgi/host_test.go
index f8abc88c897..55ca092dbca 100644
--- a/src/net/http/cgi/host_test.go
+++ b/src/net/http/cgi/host_test.go
@@ -114,7 +114,7 @@ func TestCGIBasicGet(t *testing.T) {
 		"param-a":               "b",
 		"param-foo":             "bar",
 		"env-GATEWAY_INTERFACE": "CGI/1.1",
-		"env-HTTP_HOST":         "example.com",
+		"env-HTTP_HOST":         "example.com:80",
 		"env-PATH_INFO":         "",
 		"env-QUERY_STRING":      "foo=bar&a=b",
 		"env-REMOTE_ADDR":       "1.2.3.4",
@@ -128,7 +128,7 @@ func TestCGIBasicGet(t *testing.T) {
 		"env-SERVER_PORT":       "80",
 		"env-SERVER_SOFTWARE":   "go",
 	}
-	replay := runCgiTest(t, h, "GET /test.cgi?foo=bar&a=b HTTP/1.0\nHost: example.com\n\n", expectedMap)
+	replay := runCgiTest(t, h, "GET /test.cgi?foo=bar&a=b HTTP/1.0\nHost: example.com:80\n\n", expectedMap)
 
 	if expected, got := "text/html", replay.Header().Get("Content-Type"); got != expected {
 		t.Errorf("got a Content-Type of %q; expected %q", got, expected)