diff --git a/.github/workflows/flake-update.yml b/.github/workflows/flake-update.yml
index 4c26304..fb99e9c 100644
--- a/.github/workflows/flake-update.yml
+++ b/.github/workflows/flake-update.yml
@@ -94,14 +94,13 @@ jobs:
         run: nix ./utils/eval-to-drv.sh post
       - name: Calculate diff
         run: nix ./utils/diff-evals.sh
-      - name: Read diff into environment
-        run: |
-          delimiter="$(openssl rand -hex 8)"
-          {
-          echo "POSTDIFF<<${delimiter}"
-          cat post-diff
-          echo "${delimiter}"
-          } >> $GITHUB_ENV
+      - name: Read file contents
+        id: read_file
+        uses: andstor/file-reader-action@v1
+        with:
+          path: "post-diff"
+      - name: File contents
+        run: echo "${ steps.read_file.outputs.contents }"
       - name: Write PR body template
         uses: https://github.com/DamianReeves/write-file-action@v1.3
         with:
@@ -114,7 +113,7 @@ jobs:
             ```
 
             ```
-            {{ env.POSTDIFF }}
+            {{ steps.read_file.outputs.contents }}
             ```
 
             Auto-generated by [update.yml][1] with the help of