diff --git a/exports/lakka/System.dat b/exports/lakka/System.dat
index be4a0756..a3a14e4c 100644
--- a/exports/lakka/System.dat
+++ b/exports/lakka/System.dat
@@ -167,7 +167,7 @@ game (
 	rom ( name vice/DRIVES/dos1571cr-318047-01.bin size 32768 crc F24EFCC4 md5 f9158328494b3e269f86ef419792c2e5 sha1 14ee7a0fb7e1c59c51fbf781f944387037daa3ee )
 
 	comment "Dinothawr"
-	rom ( name Dinothawr.zip size 5763199 crc 683ED4AD md5 a2e891e330d146c4046c2b622fc31462 sha1 693d8bb4d992c645e6413a57195acf4eca2f5a2e )
+	rom ( name Dinothawr.zip size 5763199 crc 683ed4ad md5 a2e891e330d146c4046c2b622fc31462 sha1 693d8bb4d992c645e6413a57195acf4eca2f5a2e )
 
 	comment "DOS"
     rom ( name MT32_CONTROL.ROM size 65536 crc A7C1531B md5 5626206284b22c2734f3e9efefcd2675 sha1 b083518fffb7f66b03c23b7eb4f868e62dc5a987 )
diff --git a/exports/retroarch/System.dat b/exports/retroarch/System.dat
index 115f2434..afb37f6e 100644
--- a/exports/retroarch/System.dat
+++ b/exports/retroarch/System.dat
@@ -168,7 +168,7 @@ game (
 	rom ( name vice/DRIVES/dos1571cr-318047-01.bin size 32768 crc F24EFCC4 md5 f9158328494b3e269f86ef419792c2e5 sha1 14ee7a0fb7e1c59c51fbf781f944387037daa3ee )
 
 	comment "Dinothawr"
-	rom ( name Dinothawr.zip size 5763199 crc 683ED4AD md5 a2e891e330d146c4046c2b622fc31462 sha1 693d8bb4d992c645e6413a57195acf4eca2f5a2e )
+	rom ( name Dinothawr.zip size 5763199 crc 683ed4ad md5 a2e891e330d146c4046c2b622fc31462 sha1 693d8bb4d992c645e6413a57195acf4eca2f5a2e )
 
 	comment "DOS"
     rom ( name MT32_CONTROL.ROM size 65536 crc A7C1531B md5 5626206284b22c2734f3e9efefcd2675 sha1 b083518fffb7f66b03c23b7eb4f868e62dc5a987 )
diff --git a/scripts/exporter/systemdat_exporter.py b/scripts/exporter/systemdat_exporter.py
index 6e403873..042a6357 100644
--- a/scripts/exporter/systemdat_exporter.py
+++ b/scripts/exporter/systemdat_exporter.py
@@ -42,6 +42,26 @@ def _quote(name: str, quoted: frozenset[str] = frozenset()) -> str:
 _ROM_NAME = re.compile(r'^(\s+)rom \( name ("[^"]+"|\S+)')
 
 
+_CRC = re.compile(r" crc (\S+)")
+
+
+def _patch(line: str, indent: str, ours: str) -> str:
+    """The original line where our values agree with it, else ours in its form.
+
+    libretro writes one crc in lower case (Dinothawr.zip's 683ed4ad) and the
+    others in upper case. A line whose values did not change keeps its bytes,
+    and a corrected crc takes the case of the line it lands on. The
+    indentation stays libretro's.
+    """
+    ours = indent + ours.lstrip("\t")
+    if line.lower() == ours.lower():
+        return line
+    theirs = _CRC.search(line)
+    if theirs and theirs.group(1) != theirs.group(1).upper():
+        ours = _CRC.sub(lambda m: f" crc {m.group(1).lower()}", ours, count=1)
+    return ours
+
+
 def _sections(original: str) -> list[tuple[str, list[str]]]:
     """The system sections of a System.dat, each comment with its rom lines."""
     _, sep, body = original.partition("\ngame (")
@@ -191,8 +211,7 @@ class Exporter(BaseExporter):
             for line in roms:
                 match = _ROM_NAME.match(line)
                 if match and match.group(2) in rendered:
-                    # The values are ours, the indentation stays libretro's.
-                    body.append(match.group(1) + rendered.pop(match.group(2)).lstrip("\t"))
+                    body.append(_patch(line, match.group(1), rendered.pop(match.group(2))))
                 else:
                     body.append(line)
             body.extend(rendered.values())
diff --git a/tests/test_exporters.py b/tests/test_exporters.py
index d0608c2c..47585e76 100644
--- a/tests/test_exporters.py
+++ b/tests/test_exporters.py
@@ -1343,6 +1343,67 @@ class SystemDatKeepsSpaceIndentedLines(unittest.TestCase):
         self.assertEqual(produced.count("kick33180.A500"), 1)
 
 
+class SystemDatComesBackAsWritten(unittest.TestCase):
+    """libretro writes one crc in lower case, Dinothawr.zip's 683ed4ad, and
+    the 513 others in upper case. Rendered upper case without condition,
+    that line changed with no correction behind it."""
+
+    SECTION = "Dinothawr"
+    ORIGINAL = (
+        'clrmamepro (\n\tname "System"\n)\n\ngame (\n\tname "System"\n'
+        '\tcomment "System"\n\n'
+        '\tcomment "Dinothawr"\n'
+        f"\trom ( name lower.zip size 10 crc 683ed4ad md5 {'1' * 32} sha1 {'1' * 40} )\n"
+        f"\trom ( name upper.zip size 10 crc 0BCDEF12 md5 {'2' * 32} sha1 {'2' * 40} )\n"
+        ")\n"
+    )
+
+    def _render(self, truth_files: list[dict]) -> str:
+        scraped = {"systems": {"dinothawr": {"native_id": self.SECTION, "files": [
+            {"name": "lower.zip", "destination": "lower.zip", "native_system": self.SECTION,
+             "size": 10, "crc32": "683ed4ad", "md5": "1" * 32, "sha1": "1" * 40},
+            {"name": "upper.zip", "destination": "upper.zip", "native_system": self.SECTION,
+             "size": 10, "crc32": "0BCDEF12", "md5": "2" * 32, "sha1": "2" * 40},
+        ]}}}
+        truth = {"systems": {"dinothawr": {"files": truth_files}}} if truth_files else {"systems": {}}
+        systems, report = build_native_model(truth, scraped)
+        return discover_exporters()["retroarch"]().render(
+            systems, report, {"System.dat": self.ORIGINAL}, None
+        )["System.dat"]
+
+    def test_an_empty_truth_hands_back_the_lines(self):
+        self.assertEqual(self._render([]), self.ORIGINAL)
+
+    def test_a_corrected_crc_follows_the_case_of_its_line(self):
+        produced = self._render([
+            {"name": "lower.zip", "size": 10, "crc32": "abcdef01", "md5": "3" * 32, "sha1": "3" * 40},
+            {"name": "upper.zip", "size": 10, "crc32": "fedcba98", "md5": "4" * 32, "sha1": "4" * 40},
+        ])
+        self.assertIn(" crc abcdef01 ", produced)
+        self.assertIn(" crc FEDCBA98 ", produced)
+
+    def test_an_added_line_takes_the_case_of_the_file(self):
+        produced = self._render([
+            {"name": "new.zip", "size": 10, "crc32": "abcdef01", "md5": "5" * 32, "sha1": "5" * 40},
+        ])
+        self.assertIn("name new.zip size 10 crc ABCDEF01 ", produced)
+
+    def test_an_empty_truth_hands_back_system_dat(self):
+        for platform in ("retroarch", "lakka"):
+            original_path = UPSTREAM_CACHE / platform / "System.dat"
+            if not original_path.exists():
+                self.skipTest("upstream cache not populated")
+            original = original_path.read_bytes()
+            exporter = discover_exporters()[platform]()
+            config = native_layer(load_platform_config(platform, str(REPO_ROOT / "platforms")))
+            systems, report = build_native_model({"systems": {}}, config)
+            produced = exporter.render(
+                systems, report, {"System.dat": original.decode("utf-8")}, config
+            )
+            with self.subTest(platform=platform):
+                self.assertEqual(produced["System.dat"].encode("utf-8"), original)
+
+
 class RommSizeIsNeverNone(unittest.TestCase):
     """size() is None where the truth contradicts RomM's hash without a size
     or names several sizes. str(None) went out as "None", validate() passed