diff --git a/exports/misterfpga.json b/exports/misterfpga.json
index 0aa1df62..ea1da06f 100644
--- a/exports/misterfpga.json
+++ b/exports/misterfpga.json
@@ -4,7 +4,8 @@
     "bios_db.json.zip": "https://raw.githubusercontent.com/ajgowans/BiosDB_MiSTer/7cfa7a3e84af078d0efba74fa46c50357c4f567c/bios_db.json.zip"
   },
   "files": [
-    "bios_db.json"
+    "bios_db.json",
+    "bios_db.json.zip"
   ],
   "summary": "81 kept, 0 added, 0 hashes corrected, 0 requirements corrected",
   "counts": {
diff --git a/exports/misterfpga/bios_db.json.zip b/exports/misterfpga/bios_db.json.zip
new file mode 100644
index 00000000..bd0b97e0
Binary files /dev/null and b/exports/misterfpga/bios_db.json.zip differ
diff --git a/scripts/export_native.py b/scripts/export_native.py
index 98ea7454..629eb03f 100644
--- a/scripts/export_native.py
+++ b/scripts/export_native.py
@@ -339,6 +339,9 @@ def collect_originals(
                 continue
             if archive:
                 originals.update(_read_archive(unpack, payload))
+                keep = getattr(exporter, "keep_archive", None)
+                if callable(keep):
+                    keep(relative, payload)
             else:
                 originals[relative] = payload.decode("utf-8", errors="replace")
         # One platform's unreadable file fails that platform: raised, it
@@ -760,7 +763,9 @@ def export_platform(
     return True, messages
 
 
-def _write_produced(root: Path, produced: dict[str, str], modes: dict[str, int]) -> None:
+def _write_produced(
+    root: Path, produced: dict[str, str | bytes], modes: dict[str, int]
+) -> None:
     """Write each file as its bytes, whole or not at all, with its mode.
 
     write_text translated line ends on Windows, so FirmwareDatabase.cs's
@@ -771,7 +776,8 @@ def _write_produced(root: Path, produced: dict[str, str], modes: dict[str, int])
     for relative, content in produced.items():
         path = root / relative
         path.parent.mkdir(parents=True, exist_ok=True)
-        write_bytes_atomic(str(path), content.encode("utf-8"))
+        data = content if isinstance(content, bytes) else content.encode("utf-8")
+        write_bytes_atomic(str(path), data)
         path.chmod(modes.get(relative, 0o644))
 
 
diff --git a/scripts/exporter/base_exporter.py b/scripts/exporter/base_exporter.py
index 31056015..b91289a0 100644
--- a/scripts/exporter/base_exporter.py
+++ b/scripts/exporter/base_exporter.py
@@ -126,6 +126,15 @@ class BaseExporter(ABC):
         """
         return True
 
+    def keep_archive(self, relative: str, payload: bytes) -> None:
+        """Hold the bytes of an original archive the render may hand back."""
+        if not hasattr(self, "_archives"):
+            self._archives: dict[str, bytes] = {}
+        self._archives[relative] = payload
+
+    def archive(self, relative: str) -> bytes | None:
+        return getattr(self, "_archives", {}).get(relative)
+
     @staticmethod
     def file_modes() -> dict[str, int]:
         """The mode of each file the platform publishes other than 0644."""
diff --git a/scripts/exporter/misterfpga_exporter.py b/scripts/exporter/misterfpga_exporter.py
index 7869a336..0d0df758 100644
--- a/scripts/exporter/misterfpga_exporter.py
+++ b/scripts/exporter/misterfpga_exporter.py
@@ -21,6 +21,27 @@ SOURCE_URL = (
 _DB_NAME = "bios_db.json"
 
 
+_ARCHIVE = "bios_db.json.zip"
+
+
+def rebuild_archive(original: bytes, member: str, text: str) -> bytes:
+    """The archive with one member's content replaced, as MiSTer writes it.
+
+    The member keeps its name, date, compression and attributes, so the
+    archive differs from MiSTer's only by the content that changed.
+    """
+    with zipfile.ZipFile(io.BytesIO(original)) as source:
+        info = source.getinfo(member)
+    rebuilt = zipfile.ZipInfo(info.filename, date_time=info.date_time)
+    rebuilt.compress_type = info.compress_type
+    rebuilt.external_attr = info.external_attr
+    rebuilt.create_system = info.create_system
+    buffer = io.BytesIO()
+    with zipfile.ZipFile(buffer, "w") as target:
+        target.writestr(rebuilt, text.encode("utf-8"))
+    return buffer.getvalue()
+
+
 class Exporter(BaseExporter):
     """Write MiSTer's bios_db.json, corrected."""
 
@@ -82,7 +103,7 @@ class Exporter(BaseExporter):
         report: Report,
         originals: dict[str, str],
         scraped: dict | None = None,
-    ) -> dict[str, str]:
+    ) -> dict[str, str | bytes]:
         original = originals.get(_DB_NAME) or originals.get("bios_db.json.zip")
         if not original:
             raise ValueError(
@@ -111,7 +132,16 @@ class Exporter(BaseExporter):
 
         # MiSTer publishes the database as one line, without a final
         # newline: written with an indent it came out as 1499 changed lines.
-        return {_DB_NAME: json.dumps(database, ensure_ascii=False)}
+        text = json.dumps(database, ensure_ascii=False)
+        produced: dict[str, str | bytes] = {_DB_NAME: text}
+        # MiSTer's Downloader fetches the archive, not the JSON in it: handed
+        # back as it came when nothing changed, rebuilt around the new
+        # member otherwise.
+        archive = self.archive(_ARCHIVE)
+        if archive is not None:
+            unchanged = text == originals.get(_DB_NAME)
+            produced[_ARCHIVE] = archive if unchanged else rebuild_archive(archive, _DB_NAME, text)
+        return produced
 
     def validate(
         self,
diff --git a/tests/test_exporters.py b/tests/test_exporters.py
index 47585e76..402b2e66 100644
--- a/tests/test_exporters.py
+++ b/tests/test_exporters.py
@@ -1546,6 +1546,45 @@ class MisterDatabaseComesBackAsWritten(unittest.TestCase):
     """The BiosDB is one line of JSON. Written with indent=2 it came out as
     1499 changed lines for a database whose content had not changed."""
 
+    def _render(self, truth: dict):
+        archive = UPSTREAM_CACHE / "misterfpga" / "bios_db.json.zip"
+        if not archive.exists():
+            self.skipTest("upstream cache not populated")
+        raw = archive.read_bytes()
+        exporter = discover_exporters()["misterfpga"]()
+        exporter.keep_archive("bios_db.json.zip", raw)
+        originals = exporter.unpack(raw)
+        config = native_layer(load_platform_config("misterfpga", str(REPO_ROOT / "platforms")))
+        systems, report = build_native_model(truth, config)
+        return raw, exporter.render(systems, report, originals, config)
+
+    def test_the_archive_mister_fetches_is_published_as_it_came(self):
+        """The Downloader fetches bios_db.json.zip, and the export gave only
+        the JSON inside it."""
+        raw, produced = self._render({"systems": {}})
+        self.assertEqual(produced["bios_db.json.zip"], raw)
+
+    def test_a_rebuilt_archive_keeps_the_member_as_mister_writes_it(self):
+        raw, _ = self._render({"systems": {}})
+        from exporter.misterfpga_exporter import rebuild_archive  # noqa: PLC0415
+
+        rebuilt = rebuild_archive(raw, "bios_db.json", '{"changed": true}')
+        with zipfile.ZipFile(io.BytesIO(raw)) as before, \
+                zipfile.ZipFile(io.BytesIO(rebuilt)) as after:
+            old, new = before.infolist()[0], after.infolist()[0]
+            self.assertEqual(after.read("bios_db.json"), b'{"changed": true}')
+            self.assertEqual(
+                (old.filename, old.date_time, old.compress_type, old.external_attr),
+                (new.filename, new.date_time, new.compress_type, new.external_attr),
+            )
+
+    def test_bytes_are_written_untouched(self):
+        import export_native  # noqa: PLC0415
+
+        with tempfile.TemporaryDirectory(dir=REPO_ROOT / "tmp") as tmp:
+            export_native._write_produced(Path(tmp), {"a.zip": b"PK\x03\x04\xff"}, {})
+            self.assertEqual((Path(tmp) / "a.zip").read_bytes(), b"PK\x03\x04\xff")
+
     def test_an_empty_truth_hands_back_the_database(self):
         archive = UPSTREAM_CACHE / "misterfpga" / "bios_db.json.zip"
         if not archive.exists():