diff --git a/build-constraints.yaml b/build-constraints.yaml
index 69342809..9918d9ac 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -70,7 +70,7 @@ packages:
         - error-or
         - error-or-utils
         - inbox
-        - mock-time
+        - mock-time < 0 # https://github.com/luntain/error-or-bundle/issues/4
 
     "Liang-Ting Chen<liang.ting.chen.tw@gmail.com> @L-TChen":
         - geniplate-mirror