diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 3888e8d44f..a79bf08563 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -155,18 +155,22 @@ jobs:
     timeout-minutes: 10
     steps:
       - name: Download all slice durations
+        # Each slice uploads the same file name (test_durations.json).
+        # With merge-multiple, the parallel downloads write to one path.
+        # This causes two problems: a race can write two JSON documents
+        # into one file, and the last write erases the other slices.
+        # Without merge-multiple, each artifact gets its own directory.
         uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
         with:
           pattern: test-durations-slice-*
           path: durations
-          merge-multiple: true
 
       - name: Merge into single durations file
         run: |
           python3 -c "
           import json, glob, os
           merged = {}
-          for f in glob.glob('durations/*test_durations.json'):
+          for f in glob.glob('durations/*/test_durations.json'):
             with open(f) as fh:
               merged.update(json.load(fh))
           with open('test_durations.json', 'w') as fh: