diff --git a/clusters/base/apps/immich/helmrelease-postgres.yaml b/clusters/base/apps/immich/helmrelease-postgres.yaml
index 02e2e66..b7e78bf 100644
--- a/clusters/base/apps/immich/helmrelease-postgres.yaml
+++ b/clusters/base/apps/immich/helmrelease-postgres.yaml
@@ -53,7 +53,12 @@ spec:
         storageClass: longhorn
         retain: true
         globalMounts:
+          # subPath, not the raw mount root: a fresh Longhorn ext4 volume's
+          # root always contains a "lost+found" dir, and postgres's initdb
+          # refuses to initialize into a non-empty directory even when
+          # lost+found is the only thing in it.
           - path: /var/lib/postgresql/data
+            subPath: data
       # postgres' parallel query workers need real shared memory, not the
       # default 64Mi container tmpfs - matches shm_size: 128mb in the
       # original docker-compose.