diff --git a/logger/datastructures.go b/logger/datastructures.go
index 474f6f7..5e74513 100644
--- a/logger/datastructures.go
+++ b/logger/datastructures.go
@@ -82,7 +82,7 @@ func (l Level) String() string {
 	case Error:
 		return "error"
 	default:
-		return string(l)
+		return fmt.Sprintf("unknown level %d", l)
 	}
 }