diff --git a/.gitea/workflows/latest.yaml b/.gitea/workflows/latest.yaml
index b5d8339..430dc43 100644
--- a/.gitea/workflows/latest.yaml
+++ b/.gitea/workflows/latest.yaml
@@ -165,7 +165,18 @@ jobs:
           git config user.name "Gitea Actions"
           git config user.email "actions@gitea.tourolle.paris"
           git fetch origin master
-          git checkout master
+          # -B against origin/master, not a bare `checkout master`. The bare
+          # form switches to the LOCAL master that actions/checkout left at the
+          # run's own SHA, so if master moved while the build ran -- and this is
+          # a nightly, so it usually has -- the manifest is edited on a stale
+          # base and the push is rejected non-fast-forward. Run 1045 failed
+          # exactly this way, having already printed "Your branch is behind
+          # 'origin/master' by 1 commit" one line before committing anyway.
+          #
+          # Resetting is right rather than merely convenient: this step appends
+          # one entry to the manifest as it stands on master, so the base it
+          # edits must be master, not whatever this build started from.
+          git checkout -B master origin/master
 
           NEW_VERSION=$(cat <<EOF
           {