diff --git a/debian/systemd/koha-common.service b/debian/systemd/koha-common.service
index 5387ee3ae5..57aacd5204 100644
--- a/debian/systemd/koha-common.service
+++ b/debian/systemd/koha-common.service
@@ -7,7 +7,9 @@ After=koha.target
 [Service]
 Type=oneshot
 RemainAfterExit=yes
-ExecStartPre=+/bin/sh -c 'for i in $(koha-list --enabled --elasticsearch 2>/dev/null); do systemctl enable --now "koha-es-indexer@$i.service" 2>/dev/null || true; done'
+# Instances can switch to Elasticsearch after their units were enabled, so
+# re-discover ES indexers on every start, like the SysV init script did.
+ExecStartPre=-/usr/sbin/koha-systemd-ctl sync-es-indexers
 ExecStart=/bin/true
 ExecStop=/bin/systemctl stop koha.target
 
diff --git a/debian/systemd/koha-systemd-ctl b/debian/systemd/koha-systemd-ctl
index ebd6b30a85..b75c3a4f4c 100755
--- a/debian/systemd/koha-systemd-ctl
+++ b/debian/systemd/koha-systemd-ctl
@@ -22,6 +22,9 @@ Commands:
   restart <instance> <svc>   Restart specific service for instance
   status <instance> <svc>    Show status of specific service for instance
 
+  sync-es-indexers           Enable and start the ES indexer for every
+                             instance configured to use Elasticsearch
+
 Services: plack, zebra, sip, z3950, worker, worker-long_tasks, indexer, es-indexer
 
 Examples:
@@ -33,6 +36,17 @@ EOF
     exit 1
 }
 
+if [ "${1:-}" = "sync-es-indexers" ]; then
+    # Which search engine an instance uses is plain koha-conf.xml state, so
+    # switching an instance to Elasticsearch never runs 'systemctl enable'.
+    # Re-discover ES instances here, like the SysV init script did on every
+    # start.
+    for instance in $(koha-list --enabled --elasticsearch 2>/dev/null); do
+        systemctl enable --now "koha-es-indexer@${instance}.service" || true
+    done
+    exit 0
+fi
+
 [ $# -lt 2 ] && usage
 
 CMD=$1