diff --git a/.github/workflows/file-freshness-pr.yml b/.github/workflows/file-freshness-pr.yml
index 99c36c8..fdd21e9 100644
--- a/.github/workflows/file-freshness-pr.yml
+++ b/.github/workflows/file-freshness-pr.yml
@@ -17,10 +17,15 @@ jobs:
         with:
           persist-credentials: false
       - name: Sync IPA codes from vocabulary repo
-        run: >
-          curl -sL 'https://raw.githubusercontent.com/publiccodeyml/italian-organizations-ipa-vocabulary/main/ipa-codes.txt'
-          | sed 's|^urn:x-italian-pa:||'
-          | LC_COLLATE=C sort > data/it/ipa_codes.txt
+        run: |
+          list="$RUNNER_TEMP/ipa-codes.txt"
+          curl -fsSL -o "$list" 'https://raw.githubusercontent.com/publiccodeyml/italian-organizations-ipa-vocabulary/main/ipa-codes.txt'
+          test -s "$list"
+          if grep -qvE '^urn:x-italian-pa:[A-Za-z0-9_]+$' "$list"; then
+            echo '::error::Unexpected line in the downloaded IPA code list'
+            exit 1
+          fi
+          sed 's|^urn:x-italian-pa:||' "$list" | LC_COLLATE=C sort > data/it/ipa_codes.txt
       - uses: peter-evans/create-pull-request@5f6978faf089d4d20b00c7766989d076bb2fc7f1 # v8
         with:
             commit-message: "chore: update it/ipa_codes.txt"