diff --git a/libguile/async.c b/libguile/async.c
index 5951f25ac..daccd0deb 100644
--- a/libguile/async.c
+++ b/libguile/async.c
@@ -155,9 +155,12 @@ scm_async_tick (void)
     scm_call_0 (scm_i_async_pop (t));
 }
 
-static const int NOT_WAITING = 0;
-static const int WAITING_ON_FD = 1;
-static const int WAITING_ON_COND = 2;
+enum
+  {
+    NOT_WAITING,
+    WAITING_ON_FD,
+    WAITING_ON_COND
+  };
 
 static inline void
 publish_wake_data_for_thread (scm_thread *t, struct scm_thread_wake_data data)