diff --git a/.github/workflows/core.yml b/.github/workflows/core.yml
index 509f962829..907137cab4 100644
--- a/.github/workflows/core.yml
+++ b/.github/workflows/core.yml
@@ -152,6 +152,9 @@ jobs:
           # but does require token for other workflows e.g. merge to `main`
           # see https://github.com/codecov/codecov-action/issues/1274#issuecomment-1934437359
           token: ${{ secrets.CODECOV_TOKEN }}
+          # downgrading after v0.7.0 broke tokenless upload
+          # see codecov/codecov-action#1487
+          version: v0.6.0
 
   build-docs:
     name: Build Sphinx docs