diff --git a/dzgui/api/mods.py b/dzgui/api/mods.py
index b8ed4b8..234835d 100644
--- a/dzgui/api/mods.py
+++ b/dzgui/api/mods.py
@@ -2,9 +2,10 @@ import hashlib
 import logging
 import re
 
-from concurrent.futures import wait
-from concurrent.futures import ThreadPoolExecutor
+from concurrent.futures import ThreadPoolExecutor, wait
+from dataclasses import dataclass
 from pathlib import Path
+from typing import Any
 
 from dzgui.api.steam import get_app_path
 from dzgui.api.servers import get_rules, fqip_to_record
@@ -17,8 +18,7 @@ from dzgui.const.constants import (
 
 from dzgui.config.query import lookup
 from dzgui.const.enum import Preferences
-
-from typing import Any
+from dzgui.init.migrate import clean_legacy_versions_file
 
 logger = logging.getLogger(APP_NAME)
 
@@ -116,10 +116,12 @@ def remove_stale_signatures(
     config: Path, versions: Path, ids: list[int] | None = None
 ) -> None:
     if versions.is_file() is False:
-        logger.warning("Creating new version signatures file")
+        logger.debug("Creating new version signatures file")
         versions.touch()
         return
 
+    clean_legacy_versions_file(versions)
+
     path = lookup(config, Preferences.DEFAULT)
     steam_path = Path(path)
     if ids is None:
diff --git a/dzgui/app_init.py b/dzgui/app_init.py
index 4903b20..96ff4d1 100644
--- a/dzgui/app_init.py
+++ b/dzgui/app_init.py
@@ -18,8 +18,8 @@ from dzgui.config.query import lookup
 from dzgui.config.userprefs import UserPrefs
 from dzgui.config.xdg import get_xdg_paths, parse_filepaths
 from dzgui.init.migrate import (
-    has_new_config,
     copy_state_files,
+    has_new_config,
     migrate_cols_file,
 )
 from dzgui.init.prereqs import has_flatpak_client, has_steam_client
diff --git a/dzgui/config/userprefs.py b/dzgui/config/userprefs.py
index a392235..d65b8b3 100644
--- a/dzgui/config/userprefs.py
+++ b/dzgui/config/userprefs.py
@@ -6,7 +6,8 @@ if TYPE_CHECKING:
     from dzgui.util.ip import Coords
 
 
-# NOTE: mutable dataclass, 'use_miles' key changes on demand
+# NOTE: mutable dataclass: 'use_miles' key changes on demand
+# 'frozen' cannot be True
 @dataclass(slots=True)
 class UserPrefs:
     is_steam_deck: bool
diff --git a/dzgui/init/migrate.py b/dzgui/init/migrate.py
index 2a5c0bc..0ff3ce2 100644
--- a/dzgui/init/migrate.py
+++ b/dzgui/init/migrate.py
@@ -1,12 +1,21 @@
 import json
+import logging
+import re
 import shutil
 
 from pathlib import Path
 from typing import Any
-from dzgui.const.constants import LEGACY_CONFIG_PATH, LEGACY_COLS_PATH, LEGACY_IPS_PATH
+from dzgui.const.constants import (
+    APP_NAME,
+    LEGACY_CONFIG_PATH,
+    LEGACY_COLS_PATH,
+    LEGACY_IPS_PATH,
+)
 from dzgui.config.convert import rc2json
 from dzgui.util._json import read_json, write_json
 
+logger = logging.getLogger(APP_NAME)
+
 
 def migrate_legacy_conf(config: Path) -> Any:
     old_conf = Path.home() / LEGACY_CONFIG_PATH
@@ -70,3 +79,15 @@ def copy_ipdb(ips_path: Path) -> None:
         return
     # TODO: ensure that month file is copied
     shutil.copy(legacy, ips_path)
+
+
+def clean_legacy_versions_file(versions: Path) -> None:
+    # NOTE: handling for #523
+    try:
+        pat = r"^(\d+),(\d+)$"
+        lines = versions.read_text().splitlines()
+        clean = [line for line in lines if re.match(pat, line)]
+        concat = "\n".join(clean)
+        versions.write_text(concat)
+    except Exception as e:
+        logger.warning(e)
diff --git a/tests/test_legacy_version_file.py b/tests/test_legacy_version_file.py
new file mode 100644
index 0000000..3117b37
--- /dev/null
+++ b/tests/test_legacy_version_file.py
@@ -0,0 +1,25 @@
+from typing import TYPE_CHECKING
+
+from dzgui.init.migrate import clean_legacy_versions_file
+
+if TYPE_CHECKING:
+    from pathlib import Path
+
+
+def test_null_signature_stripping(tmp_path: "Path") -> None:
+    tmp = tmp_path.joinpath("dzg.versions")
+    lines = [
+        "1111,2222",
+        "3333,4444",
+        "5555,null",
+        "foo",
+        ",4555",
+        "1111",
+        " ",
+        ",,,",
+        "-1",
+    ]
+    expect = ["1111,2222", "3333,4444"]
+    tmp.write_text("\n".join(lines))
+    clean_legacy_versions_file(tmp)
+    assert expect == tmp.read_text().splitlines()