diff --git a/scripts/check_file_sizes.py b/scripts/check_file_sizes.py
index 7c4d10d..543fb9c 100644
--- a/scripts/check_file_sizes.py
+++ b/scripts/check_file_sizes.py
@@ -39,7 +39,8 @@ def main() -> int:
     allowed = allowlist()
     problems = []
     for path in tracked_sources():
-        lines = Path(path).read_text(encoding="utf-8", errors="replace").count("\n")
+        text = Path(path).read_text(encoding="utf-8", errors="replace")
+        lines = len(text.splitlines())
         ceiling = allowed.pop(path, None)
         if ceiling is None and lines > LIMIT:
             problems.append(f"{path}: {lines} lines, limit {LIMIT}. Split it by concern.")
diff --git a/systemgate/config.py b/systemgate/config.py
index 6977142..3936f16 100644
--- a/systemgate/config.py
+++ b/systemgate/config.py
@@ -22,13 +22,28 @@ def _value(name: str, default: str = "") -> str:
     return os.environ.get(name, default).strip()
 
 
+class ConfigError(ValueError):
+    pass
+
+
+def _port(name: str, default: str) -> int:
+    raw = _value(name, default)
+    try:
+        port = int(raw)
+    except ValueError:
+        raise ConfigError(f"invalid {name}: {raw!r} (expected integer 1-65535)") from None
+    if not 1 <= port <= 65535:
+        raise ConfigError(f"{name} out of range: {port} (expected 1-65535)")
+    return port
+
+
 def get_settings() -> Settings:
     root = Path(__file__).resolve().parents[1]
     data_dir = Path(_value("SYSTEMGATE_DATA_DIR", str(root / "data"))).expanduser().resolve()
     backup_root = Path(_value("SYSTEMGATE_BACKUP_ROOT", "/backups")).expanduser().resolve()
     return Settings(
         host=_value("SYSTEMGATE_HOST", "127.0.0.1"),
-        port=int(_value("SYSTEMGATE_PORT", "8040")),
+        port=_port("SYSTEMGATE_PORT", "8040"),
         data_dir=data_dir,
         admin_key=_value("SYSTEMGATE_ADMIN_KEY"),
         backup_root=backup_root,