diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d7426af..2c3e56e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -73,6 +73,7 @@ jobs:
         with:
           enable-cache: false
       - name: Create Python virtual environment
+        id: create-venv
         if: steps.cache-venv.outputs.cache-hit != 'true'
         env:
           AIOHTTP_NO_EXTENSIONS: 1
@@ -94,7 +95,12 @@ jobs:
             uv pip install pytest-xdist
           fi
       - name: Cache base Python virtual environment
-        if: steps.cache-venv.outputs.cache-hit != 'true'
+        # Use `always()` so a cancellation (e.g. fail-fast from a sibling
+        # matrix job, or a concurrency cancel) cannot interrupt the save
+        # mid-upload and leave the cache key reserved but unpopulated.
+        # Guard on `create-venv` success so a failed/cancelled venv build
+        # is never cached.
+        if: always() && steps.create-venv.outcome == 'success'
         uses: actions/cache/save@v5
         with:
           path: .venv