diff --git a/.github/workflows/pages.yml b/.github/workflows/pages.yml
index f347dfc..d0449fb 100644
--- a/.github/workflows/pages.yml
+++ b/.github/workflows/pages.yml
@@ -35,7 +35,7 @@ jobs:
         run: |
           spectaql --introspection-url https://timdex.mit.edu/graphql -e -t ./docs/reference docs/reference/_spectaql_config.yml
       - name: Build with Jekyll
-        uses: actions/jekyll-build-pages@v1
+        uses: actions/jekyll-build-pages@44a6e6beabd48582f863aeeb6cb2151cc1716697 # v1
         with:
           source: ./docs
           destination: ./_site
diff --git a/Dockerfile b/Dockerfile
index 54046aa..90f7ed1 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM ruby:2.6.5-alpine
+FROM ruby:2.6.5-alpine@sha256:a5b974e2ebb2b72642f4de4e5562597ec0883c3bfd93e9553cee6bd395dfbf00
 RUN mkdir /timdex
 WORKDIR /timdex
 COPY Gemfile /timdex/Gemfile