diff --git a/src/encoding/nfd-constants.hpp b/src/encoding/nfd-constants.hpp
index 7026898..8b57def 100644
--- a/src/encoding/nfd-constants.hpp
+++ b/src/encoding/nfd-constants.hpp
@@ -99,7 +99,7 @@
 
 /** \ingroup management
  */
-enum RouteFlags {
+enum RouteFlags : uint64_t {
   ROUTE_FLAGS_NONE         = 0,
   ROUTE_FLAG_CHILD_INHERIT = 1,
   ROUTE_FLAG_CAPTURE       = 2,