diff --git a/.buildkite/hooks/post-command b/.buildkite/hooks/post-command
index 2e88eaf13..aa7b50e43 100644
--- a/.buildkite/hooks/post-command
+++ b/.buildkite/hooks/post-command
@@ -77,8 +77,11 @@ done
 set -euo pipefail
 
 # Remove all Docker runtimes that may be installed.
-if grep -qE runtimes /etc/docker/daemon.json; then
-  cat /etc/docker/daemon.json | jq 'del(.runtimes) + {runtimes: {}}' \
+num_docker_runtimes="$(jq \
+    '(if has("runtimes") then .runtimes else {} end) | length' \
+    < /etc/docker/daemon.json)"
+if [[ "$num_docker_runtimes" -gt 0 ]]; then
+  cat /etc/docker/daemon.json | jq 'del(.runtimes)' \
     | sudo tee /etc/docker/daemon.json.tmp
   sudo mv /etc/docker/daemon.json.tmp /etc/docker/daemon.json
   bash -c "$DOCKER_RELOAD_COMMAND"