diff --git a/app/cmd/server.go b/app/cmd/server.go
index 3da748d7bd..a4b8470940 100644
--- a/app/cmd/server.go
+++ b/app/cmd/server.go
@@ -804,6 +804,9 @@ func (c *serverConfig) fillMasqHandler(hyConfig *server.Config) error {
 		if err != nil {
 			return configError{Field: "masquerade.proxy.url", Err: err}
 		}
+		if u.Scheme != "http" && u.Scheme != "https" {
+			return configError{Field: "masquerade.proxy.url", Err: fmt.Errorf("unsupported protocol scheme \"%s\"", u.Scheme)}
+		}
 		handler = &httputil.ReverseProxy{
 			Rewrite: func(r *httputil.ProxyRequest) {
 				r.SetURL(u)