diff --git a/restart_prompt.md b/restart_prompt.md
index cba6a53..f82e0bd 100644
--- a/restart_prompt.md
+++ b/restart_prompt.md
@@ -85,6 +85,7 @@ Historical sorting:
 - Account selection is explicit with `--account <naam>`, for example `--account backup`.
 - `--audit` is available in dry-run mode.
 - It logs to `verplaats_log.json`, retries IMAP aborts where implemented, and parses FETCH responses defensively.
+- Header parsing now guards against non-bytes FETCH payloads in both step 2 and step 3 so a malformed/odd IMAP response is logged as a failed header fetch instead of aborting the whole run.
 
 Folder creation:
 
@@ -228,6 +229,8 @@ Totaal gepland: 0 | Totaal geen match: 2218 | Totaal overgeslagen: 8219 | Totaal
 
 Treat that as a successful backup historical-sorter run with no immediate recovery work needed.
 
+A later local `verplaats_bestaand.log` in the workspace is not a `hans` audit. It shows a real `backup` execution (`LET OP`, `Account: backup`) that aborted at `INBOX.Bestellingen.PostNL` with `AttributeError: 'int' object has no attribute 'decode'`. The visible partial counters before the crash were 74 folder summaries, 5,921 planned, 5,920 moved, 3,105 no match, 1,765 skipped, and 1 error. Do not treat this log as approval to run the real `hans` mailbox move.
+
 ## Verification Commands
 
 Latest local verification included:
@@ -241,6 +244,7 @@ git diff --check
 ```
 
 After the plain-mode stop wrapper change, `bash -n deploy_vps.sh` was rerun successfully.
+After the historical-sorter header guard change, `python3 -m py_compile verplaats_bestaand.py` was rerun successfully.
 
 Useful routing sanity check:
 
diff --git a/verplaats_bestaand.py b/verplaats_bestaand.py
index 44228bd..e9738e2 100644
--- a/verplaats_bestaand.py
+++ b/verplaats_bestaand.py
@@ -372,6 +372,19 @@ def stap2_bronmappen_routing(session: ImapSession, log: dict, dry: bool):
                 mislukt += 1
                 log_failure(log, "stap2", bron, uid, None, "fetch_header", status, data)
                 continue
+            if not isinstance(raw_header, bytes):
+                mislukt += 1
+                log_failure(
+                    log,
+                    "stap2",
+                    bron,
+                    uid,
+                    None,
+                    "fetch_header_type",
+                    status,
+                    f"expected bytes, got {type(raw_header).__name__}",
+                )
+                continue
 
             msg = email.message_from_bytes(raw_header)
             from_raw = decode_hdr(msg.get("From", ""))
@@ -502,6 +515,19 @@ def stap3_facturen(session: ImapSession, log: dict, dry: bool):
                 mislukt += 1
                 log_failure(log, "stap3", bron, uid, None, "fetch_header", status, data)
                 continue
+            if not isinstance(raw_header, bytes):
+                mislukt += 1
+                log_failure(
+                    log,
+                    "stap3",
+                    bron,
+                    uid,
+                    None,
+                    "fetch_header_type",
+                    status,
+                    f"expected bytes, got {type(raw_header).__name__}",
+                )
+                continue
 
             msg      = email.message_from_bytes(raw_header)
             date_str = msg.get("Date", "")