diff --git a/.github/workflows/stack.yml b/.github/workflows/stack.yml
index ffc27ab..7958791 100644
--- a/.github/workflows/stack.yml
+++ b/.github/workflows/stack.yml
@@ -25,6 +25,12 @@ jobs:
       - name: Clone project
         uses: actions/checkout@v2
 
+      - name: Prepare apt sources
+        run: |
+          set -ex
+          sudo add-apt-repository -y ppa:hvr/ghc
+          sudo apt update -y
+
       - name: Install C dependencies
         run: |
           set -ex