diff --git a/scripts/exporter/retrobat_exporter.py b/scripts/exporter/retrobat_exporter.py
index 04d4c133..1f014a91 100644
--- a/scripts/exporter/retrobat_exporter.py
+++ b/scripts/exporter/retrobat_exporter.py
@@ -66,33 +66,42 @@ class Exporter(BaseExporter):
         originals: dict[str, str],
         scraped: dict | None = None,
     ) -> dict[str, str]:
-        # Keep the platform's own key order when we have its file, so the
-        # diff a maintainer reads is the corrections and nothing else.
-        order: list[str] = []
+        # The platform's own file is the base: its key and entry order stay,
+        # so the diff a maintainer reads is the corrections and nothing else,
+        # and a system or file our transcription does not carry (RetroBat
+        # renamed ic10_g24lc64 after a scrape) is kept as RetroBat wrote it.
+        base: dict = {}
         original = originals.get(self.native_filename(), "")
         if original:
             try:
-                order = list(json.loads(original))
+                base = json.loads(original, object_pairs_hook=OrderedDict)
             except json.JSONDecodeError:
-                order = []
+                base = {}
 
         exportable = {
             system.native_id: (system, files)
             for system, files in self.exportable(systems, require="md5")
         }
-        keys = [k for k in order if k in exportable]
-        keys.extend(sorted(k for k in exportable if k not in keys))
+        keys = list(base)
+        keys.extend(sorted(k for k in exportable if k not in base))
 
         output: OrderedDict[str, object] = OrderedDict()
         for key in keys:
+            if key not in exportable:
+                output[key] = base[key]
+                continue
             system, files = exportable[key]
-            bios_files = []
+            ours: OrderedDict[str, OrderedDict[str, str]] = OrderedDict()
             for fe in files:
                 entry: OrderedDict[str, str] = OrderedDict()
                 entry["md5"] = self._md5(fe)
                 declared = fe.native("native_path", "")
                 entry["file"] = str(declared) if declared else f"bios/{fe.destination}"
-                bios_files.append(entry)
+                ours.setdefault(entry["file"], entry)
+            bios_files = []
+            for theirs in (base.get(key) or {}).get("biosFiles", []):
+                bios_files.append(ours.pop(theirs.get("file"), theirs))
+            bios_files.extend(ours.values())
             system_entry: OrderedDict[str, object] = OrderedDict()
             system_entry["name"] = self.display_name(system)
             system_entry["biosFiles"] = bios_files
diff --git a/tests/test_export_counts.py b/tests/test_export_counts.py
index e4df63c9..6ed3a51a 100644
--- a/tests/test_export_counts.py
+++ b/tests/test_export_counts.py
@@ -148,6 +148,39 @@ class HashesTheFormatCannotHold(unittest.TestCase):
         self.assertFalse(EmuDeck().states(unhashed, "md5"))
 
 
+class RetroBatKeepsWhatWeDoNotModel(unittest.TestCase):
+    """RetroBat renamed chihiro/ic10_g24lc64 to ic10_g24lc64.bin after our
+    scrape. The export was rebuilt from our model and read the original only
+    for its key order, so the renamed entry vanished from RetroBat's file,
+    and a system we do not carry would have vanished whole."""
+
+    def test_an_unmodelled_file_and_system_stay_as_written(self):
+        modelled = NativeFile(
+            "ic11_24lc024.bin", "chihiro/ic11_24lc024.bin", "chihiro",
+            platform={"md5": "", "native_path": "bios/chihiro/ic11_24lc024.bin"},
+            truth={"md5": A}, filled=["md5"],
+        )
+        systems = {"chihiro": NativeSystem("chihiro", files=[modelled])}
+        original = {
+            "chihiro": {"name": "Sega Chihiro", "biosFiles": [
+                {"md5": "", "file": "bios/chihiro/ic10_g24lc64.bin"},
+                {"md5": "", "file": "bios/chihiro/ic11_24lc024.bin"},
+            ]},
+            "newsys": {"name": "New", "biosFiles": [{"md5": B, "file": "bios/new.bin"}]},
+        }
+        from exporter.baseline import Report
+
+        produced = json.loads(RetroBat().render(
+            systems, Report(), {"batocera-systems.json": json.dumps(original)},
+        )["batocera-systems.json"])
+        self.assertEqual(list(produced), ["chihiro", "newsys"])
+        self.assertEqual(produced["newsys"], original["newsys"])
+        self.assertEqual(produced["chihiro"]["biosFiles"], [
+            {"md5": "", "file": "bios/chihiro/ic10_g24lc64.bin"},
+            {"md5": A, "file": "bios/chihiro/ic11_24lc024.bin"},
+        ])
+
+
 class EmuDeckWritesItsCorrections(unittest.TestCase):
     """A correction replaced nothing: every withdrawal was refused, the run
     counted the correction anyway and validate failed on it."""