diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 65b838a8..20563b5a 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -44,6 +44,7 @@ jobs:
         install: >-
           git
           make
+          diffutils
 
     - name: Run tests (Linux)
       if: matrix.os == 'ubuntu-latest'