diff --git a/.github/workflows/unsoundness.yml b/.github/workflows/unsoundness.yml
index 3d4491cf7..457376d5a 100644
--- a/.github/workflows/unsoundness.yml
+++ b/.github/workflows/unsoundness.yml
@@ -34,5 +34,7 @@ jobs:
       - uses: Swatinem/rust-cache@v2
         with:
           prefix-key: v0-miri
+      - name: Install CapnProto
+        run: sudo apt-get install -y capnproto
       - name: Test with Miri
         run: cargo miri test