diff --git a/build-constraints.yaml b/build-constraints.yaml
index ae6aeea2..418e5bde 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -2574,6 +2574,8 @@ packages:
         - hw-prim ==0.1.0.3
         - hw-bits ==0.1.0.1
 
+        # https://github.com/fpco/stackage/issues/1959
+        - megaparsec < 5.1.0
 # end of packages