diff --git a/.aqua/aqua.yaml b/.aqua/aqua.yaml
index cfa4885e..58e3f86d 100644
--- a/.aqua/aqua.yaml
+++ b/.aqua/aqua.yaml
@@ -20,7 +20,4 @@ packages:
   # --- farcloser tools (local registry; standard once registered upstream) ---
   - name: farcloser/limen@v0.8.0 # renovate: depName=farcloser/limen
     registry: local
-  # ossein provides `docker` for the linux legs of build-posix.sh (see there).
-  - name: farcloser/ossein@v0.3.0 # renovate: depName=farcloser/ossein
-    registry: local
   - import: ../.limen/aqua.yaml
diff --git a/build-posix.sh b/build-posix.sh
index 510aa972..7220d5ec 100755
--- a/build-posix.sh
+++ b/build-posix.sh
@@ -12,8 +12,10 @@
 # workflow. The mac leg runs directly on a macOS machine (their script
 # provisions its homebrew dependencies).
 #
-# The container runtime is `docker`, from the hermetic PATH like every other
-# tool, on every host. The amd64 leg on an arm64 mac runs under Rosetta
+# The container runtime is `docker`. On a Mac it is ossein's, which limen's
+# base tool set puts on the hermetic PATH ahead of any Docker installed there;
+# ossein is darwin/arm64 only, so on a linux host (CI's linux legs) it is the
+# machine's own docker. The amd64 leg on an arm64 mac runs under Rosetta
 # (--platform linux/amd64).
 #
 # Usage: build-posix.sh {linux-amd64|linux-arm64|mac-arm64}