diff --git a/ci/config.cabal.project b/ci/config.cabal.project
index 48340dcfa16e0e674823ef8390d13a93d2a82caa..c894c0d2a39220a89d3285c14cf039480ad33ff3 100644
--- a/ci/config.cabal.project
+++ b/ci/config.cabal.project
@@ -9,3 +9,7 @@ constraints: uvector == 0.0
 
 -- containers-0.5 generally won't build with any recent compiler
 constraints: containers >= 0.6
+
+-- earlier transformers-compat versions don't include the Eq constraint on Eq1
+-- instances needed by GHC 9.6
+constraints: transformers-compat >= 0.7