diff --git a/build-constraints.yaml b/build-constraints.yaml
index 4b283655..0c8ac467 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -1712,7 +1712,7 @@ packages:
 
     "Will Coster <willcoster@gmail.com> @fimad":
         - prometheus-client
-        - prometheus-metrics-ghc
+        - prometheus-metrics-ghc < 0 # Build failure: https://github.com/fimad/prometheus-haskell/issues/39
         - scalpel
         - scalpel-core
         - wai-middleware-prometheus < 0 # GHC 8.4 via prometheus-client