diff --git a/build-constraints.yaml b/build-constraints.yaml
index a993d839..f723bb55 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -3534,7 +3534,7 @@ packages:
         - pier-core < 0
         - pier < 0
         - haskeline < 0.8 # https://github.com/commercialhaskell/stackage/issues/5269
-        - ghc-source-gen
+        - ghc-source-gen < 0.4 # https://github.com/commercialhaskell/stackage/issues/5400
 
     "Christof Schramm <christof.schramm@campus.lmu.de>":
         - mnist-idx