diff --git a/os2.rkt b/os2.rkt
index 272232c..4a9c8ee 100644
--- a/os2.rkt
+++ b/os2.rkt
@@ -479,7 +479,8 @@
     (match (run-vm state)
       [(transition state actions)
        (when (not (null? actions))
-	 (error 'ground-vm "No meta-actions available in ground-vm: ~v" actions))
+	 (error 'ground-vm "Cannot process meta-actions because no further meta-level exists: ~v"
+		actions))
        (define waiting? (null? (vm-pending-actions state)))
        (define active-events
 	 (for*/fold ([acc '()])