diff --git a/README.md b/README.md
index 61fe7c6..b6c5263 100644
--- a/README.md
+++ b/README.md
@@ -103,7 +103,7 @@ sudo systemctl status vw-eu-data-act-exporter
 | `vins` | List of vehicle VINs to scrape |
 | `scrape_interval_minutes` | Poll interval per vehicle. The portal only delivers new datasets for "continuous" data requests roughly every ~15 min anyway - a shorter interval will not yield fresher data, but will increase the login frequency against the account |
 | `persist_raw_json` | `False` by default. When set to `True`, the JSON extracted from every downloaded dataset is written to disk (one file per VIN per scrape), including the JSON extracted from `_no_content_found.zip` placeholders when they carry one. ZIP files are never written to disk, only the extracted JSON - useful while tuning the field mapping in `vw-eu-data-act-exporter.py`. Not needed for normal operation |
-| `persist_raw_json_dir` | Directory the raw JSON files are written to when `persist_raw_json` is enabled (default: `./raw_json`, relative to the working directory) |
+| `persist_raw_json_dir` | Directory the raw JSON files are written to when `persist_raw_json` is enabled. Defaults to `$STATE_DIRECTORY` (set automatically by the systemd unit's `StateDirectory=vw-eu-data-act-exporter`, i.e. `/var/lib/vw-eu-data-act-exporter`), falling back to `./raw_json` for ad-hoc/local runs outside systemd |
 
 Prerequisite in the portal (one-time, in a browser): connect vehicle ->
 "Get customised data" -> enable continuous, 15-minute frequency (see the
@@ -136,3 +136,11 @@ be independent of, and significantly shorter than, `scrape_interval_minutes`
 - `WARNING ... Unknown enum value`: a new, not-yet-listed value for an enum
   metric - the state is exported as `UNKNOWN`, extend the list in the
   source code if needed.
+- Service fails immediately with `status=226/NAMESPACE` /
+  `Failed to set up mount namespacing`: usually a stale unit file from
+  before `StateDirectory=` was introduced (e.g. still using
+  `ReadWritePaths=.../raw_json` pointing at a directory that was never
+  created). Re-copy the current `vw-eu-data-act-exporter.service`, run
+  `sudo systemctl daemon-reload`, and restart - `StateDirectory=` makes
+  systemd create that directory (with correct ownership) itself, no manual
+  `mkdir`/`chown` needed.
diff --git a/config.py b/config.py
index ef11a60..9c3c2a5 100644
--- a/config.py
+++ b/config.py
@@ -48,7 +48,10 @@ scrape_interval_minutes = 15
 # carry one. ZIP files themselves are never written to disk. Disabled by
 # default, since the exporter is designed to be stateless (see README.md).
 persist_raw_json = False
-persist_raw_json_dir = "./raw_json"
+# Under the systemd unit, StateDirectory=vw-eu-data-act-exporter makes
+# systemd export $STATE_DIRECTORY (an already-created, correctly-owned
+# directory) - fall back to a relative path for ad-hoc/local runs.
+persist_raw_json_dir = os.environ.get("STATE_DIRECTORY", "./raw_json")
 
 # --- Logging ---------------------------------------------------------------
 log_level = "INFO"
diff --git a/vw-eu-data-act-exporter.service b/vw-eu-data-act-exporter.service
index 8cdf2e1..7362885 100644
--- a/vw-eu-data-act-exporter.service
+++ b/vw-eu-data-act-exporter.service
@@ -13,7 +13,13 @@ Restart=on-failure
 RestartSec=30
 
 # Hardening
-ReadWritePaths=/opt/vw-eu-data-act-exporter/raw_json
+# StateDirectory is created automatically (with correct ownership) before
+# the service starts and is writable under ProtectSystem=strict without a
+# ReadWritePaths= entry - systemd exposes its absolute path via
+# $STATE_DIRECTORY, which config.py picks up for persist_raw_json_dir.
+# Unlike ReadWritePaths=, this does not require the directory to already
+# exist on disk.
+StateDirectory=vw-eu-data-act-exporter
 NoNewPrivileges=true
 ProtectSystem=strict
 ProtectHome=true