diff --git a/stack.yaml b/stack.yaml
index c05ecb3b0e..59abff99db 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -21,5 +21,6 @@ packages:
 resolver: lts-5.18
 extra-deps:
 - process-1.3.0.0
+- concurrent-output-1.7.7
 explicit-setup-deps:
   git-annex: true