diff --git a/.github/workflows/R-CMD-check.yaml b/.github/workflows/R-CMD-check.yaml
index 2d0280b8..4ffe1f13 100644
--- a/.github/workflows/R-CMD-check.yaml
+++ b/.github/workflows/R-CMD-check.yaml
@@ -52,7 +52,7 @@ jobs:
       - name: setup server
         if: runner.os != 'macOS'
         run: |
-          cargo install --git https://github.com/mrc-ide/outpack_server --branch main
+          cargo install --git https://github.com/mrc-ide/outpack_server --branch main --locked
 
       - uses: r-lib/actions/setup-r-dependencies@v2
         with:
diff --git a/.github/workflows/test-coverage.yaml b/.github/workflows/test-coverage.yaml
index 45b00a2e..6fd6f34f 100644
--- a/.github/workflows/test-coverage.yaml
+++ b/.github/workflows/test-coverage.yaml
@@ -23,7 +23,7 @@ jobs:
 
       - name: setup server
         run: |
-          cargo install --git https://github.com/mrc-ide/outpack_server --branch main
+          cargo install --git https://github.com/mrc-ide/outpack_server --branch main --locked
 
       - uses: r-lib/actions/setup-r-dependencies@v2
         with: