diff --git a/main.go b/main.go
index c3afed3..796fae4 100644
--- a/main.go
+++ b/main.go
@@ -47,6 +47,7 @@ func (t Tool) execute(in io.Reader, w http.ResponseWriter) {
 	cmd.Stdout = buf
 
 	if e := cmd.Run(); e == nil {
+		w.Header().Set("Content-Type", "image/svg+xml")
 		io.Copy(w, buf)
 	} else {
 		log.Printf("%s returned error\n", t.Name)