diff --git a/serve.go b/serve.go
index 06fa10f..d90324e 100644
--- a/serve.go
+++ b/serve.go
@@ -27,6 +27,7 @@ func index(w http.ResponseWriter, r *http.Request) {
 		options["MonteCarlo"] = mcOpt
 		options["ClosedForm"] = bsOpt
 
+		w.Header().Set("Content-Type", "application/json")
 		json.NewEncoder(w).Encode(options)
 
 	} else if r.Method == "GET" {