diff --git a/build-constraints.yaml b/build-constraints.yaml
index 43dc41cc..0342b9f4 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -3014,7 +3014,7 @@ packages:
     "Justus Adam <dev@justus.science> @JustusAdam":
         - marvin
         - marvin-interpolate
-        - mustache
+        - mustache < 2.4.0 # https://github.com/commercialhaskell/stackage/issues/6421
         - exit-codes >= 1.0.0
 
     "Cindy Wang <cindylinz@gmail.com> @CindyLinz":