diff --git a/build-constraints.yaml b/build-constraints.yaml
index 415f1f95..3e70909e 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -1392,6 +1392,7 @@ packages:
 
     "Joachim Breitner <mail@joachim-breitner.de> @nomeata":
         - arbtt
+        - rec-def
         - bytestring-progress # dependency of arbtt
         - circle-packing
         - haskell-spacegoo