diff --git a/build-constraints.yaml b/build-constraints.yaml
index 2237837a..2b50ccc2 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -3043,6 +3043,7 @@ packages:
         - arithmoi
         - bitvec
         - poly
+        - extended-reals
 
     "Ashley Yakeley <ashley@semantic.org> @AshleyYakeley":
         - countable