diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index c02f8fe..62fb77b 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -31,7 +31,7 @@ jobs:
 
     steps:
     - name: Check out this repository
-      uses: actions/checkout@v3
+      uses: actions/checkout@f43a0e5ff2bd294095638e18286ca9a3d1956744  # v3
 
     - name: Setup Elixir and Erlang
       uses: erlef/setup-beam@5304e04ea2b355f03681464e683d92e3b2f18451 # v1.18.2
@@ -42,7 +42,7 @@ jobs:
     # We need to manually restore and then save, so that we can save the "_build" directory
     # *without* the Elixir compiled code in it.
     - name: Restore Mix dependencies cache
-      uses: actions/cache/restore@v3
+      uses: actions/cache/restore@6f8efc29b200d32929f49075959781ed54ec270c  # v3
       id: mix-deps-cache
       with:
         path: |
@@ -58,7 +58,7 @@ jobs:
       run: mix do deps.get, deps.compile
 
     - name: Save Mix dependencies cache
-      uses: actions/cache/save@v3
+      uses: actions/cache/save@6f8efc29b200d32929f49075959781ed54ec270c  # v3
       if: steps.mix-deps-cache.outputs.cache-hit != 'true'
       with:
         path: |