diff --git a/build-constraints.yaml b/build-constraints.yaml
index 12e44f7c..c3b32447 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -313,7 +313,7 @@ packages:
 
         # @ghorn
         - not-gloss
-        - spatial-math < 0.3
+        - spatial-math < 0.3 # Only older versions works on recent GHCs.
 
     "Phil de Joux <phil.dejoux@blockscope.com> @philderbeast":
         - siggy-chardust