diff --git a/server/server.go b/server/server.go
index 7d77d7d..49d5f85 100644
--- a/server/server.go
+++ b/server/server.go
@@ -71,6 +71,11 @@ func (srv *server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		w.Write(errRes.ErrorResponse())
 		srv.logger.Logf(log.LevelError, "request failed: %s", errRes.String())
 	}
-	w.WriteHeader(res.HttpStatus())
+	if res.HttpStatus() >= 100 {
+		w.WriteHeader(res.HttpStatus())
+	} else {
+		w.WriteHeader(http.StatusInternalServerError)
+		srv.logger.Logf(log.LevelError, "received invalid status from service (%d)", res.HttpStatus())
+	}
 	w.Write(res.Response())
 }