diff --git a/lib/lsp-devtools/changes/130.fix.md b/lib/lsp-devtools/changes/130.fix.md
new file mode 100644
index 0000000..2c810b2
--- /dev/null
+++ b/lib/lsp-devtools/changes/130.fix.md
@@ -0,0 +1 @@
+The `lsp-devtools record` command will now produce valid JSON when using the `--to-file` option without an explicitly provided format string.
diff --git a/lib/lsp-devtools/lsp_devtools/record/__init__.py b/lib/lsp-devtools/lsp_devtools/record/__init__.py
index 2f66f32..6d51f43 100644
--- a/lib/lsp-devtools/lsp_devtools/record/__init__.py
+++ b/lib/lsp-devtools/lsp_devtools/record/__init__.py
@@ -78,7 +78,7 @@ def log_rpc_message(ls: AgentServer, message: MessageText):
     parse_rpc_message(ls, message, logfn)
 
 
-def setup_stdout_output(args) -> Console:
+def setup_stdout_output(args, logger: logging.Logger) -> Console:
     """Log to stdout."""
 
     console = Console(record=args.save_output is not None)
@@ -90,7 +90,7 @@ def setup_stdout_output(args) -> Console:
             exclude_message_types=args.exclude_message_types,
             include_methods=args.include_methods,
             exclude_methods=args.exclude_methods,
-            formatter=args.format_message,
+            formatter=args.format_message or "{.|json}",
         )
     )
 
@@ -98,7 +98,7 @@ def setup_stdout_output(args) -> Console:
     return console
 
 
-def setup_file_output(args):
+def setup_file_output(args, logger: logging.Logger):
     handler = logging.FileHandler(filename=str(args.to_file))
     handler.setLevel(logging.INFO)
     handler.addFilter(
@@ -108,14 +108,14 @@ def setup_file_output(args):
             exclude_message_types=args.exclude_message_types,
             include_methods=args.include_methods,
             exclude_methods=args.exclude_methods,
-            formatter=args.format_message,
+            formatter=args.format_message or "{.|json-compact}",
         )
     )
 
     logger.addHandler(handler)
 
 
-def setup_sqlite_output(args):
+def setup_sqlite_output(args, logger: logging.Logger):
     handler = SqlHandler(args.to_sqlite)
     handler.setLevel(logging.INFO)
     handler.addFilter(
@@ -142,13 +142,13 @@ def start_recording(args, extra: List[str]):
     port = args.port
 
     if args.to_file:
-        setup_file_output(args)
+        setup_file_output(args, logger)
 
     elif args.to_sqlite:
-        setup_sqlite_output(args)
+        setup_sqlite_output(args, logger)
 
     else:
-        console = setup_stdout_output(args)
+        console = setup_stdout_output(args, logger)
 
     try:
         print(f"Waiting for connection on {host}:{port}...", end="\r", flush=True)
@@ -266,7 +266,7 @@ def cli(commands: argparse._SubParsersAction):
     format.add_argument(
         "-f",
         "--format-message",
-        default="",
+        default=None,
         help=(
             "format messages according to given format string, "
             "see example commands above for syntax. "
diff --git a/lib/lsp-devtools/tests/record/test_record.py b/lib/lsp-devtools/tests/record/test_record.py
new file mode 100644
index 0000000..cb6d862
--- /dev/null
+++ b/lib/lsp-devtools/tests/record/test_record.py
@@ -0,0 +1,123 @@
+from __future__ import annotations
+
+import argparse
+import logging
+import typing
+
+import pytest
+
+from lsp_devtools.record import cli
+from lsp_devtools.record import setup_file_output
+
+if typing.TYPE_CHECKING:
+    import pathlib
+    from typing import Any
+    from typing import Dict
+    from typing import List
+
+
+@pytest.fixture(scope="module")
+def record():
+    """Return a cli parser for the record command."""
+    parser = argparse.ArgumentParser(description="for testing purposes")
+    commands = parser.add_subparsers()
+    cli(commands)
+
+    return parser
+
+
+@pytest.fixture()
+def logger():
+    """Return the logger instance to use."""
+
+    log = logging.getLogger(__name__)
+    log.setLevel(logging.INFO)
+
+    for handler in log.handlers:
+        log.removeHandler(handler)
+
+    return log
+
+
+@pytest.mark.parametrize(
+    "args, messages, expected",
+    [
+        (
+            [],
+            [dict(jsonrpc="2.0", id=1, method="initialize", params=dict())],
+            '{"jsonrpc": "2.0", "id": 1, "method": "initialize", "params": {}}\n',
+        ),
+        (
+            ["-f", "{.|json-compact}"],
+            [dict(jsonrpc="2.0", id=1, method="initialize", params=dict())],
+            '{"jsonrpc": "2.0", "id": 1, "method": "initialize", "params": {}}\n',
+        ),
+        (
+            ["-f", "{.|json}"],
+            [dict(jsonrpc="2.0", id=1, method="initialize", params=dict())],
+            "\n".join(
+                [
+                    "{",
+                    '  "jsonrpc": "2.0",',
+                    '  "id": 1,',
+                    '  "method": "initialize",',
+                    '  "params": {}',
+                    "}",
+                    "",
+                ]
+            ),
+        ),
+        (
+            ["-f", "{.method|json}"],
+            [
+                dict(jsonrpc="2.0", id=1, method="initialize", params=dict()),
+                dict(jsonrpc="2.0", id=1, result=dict()),
+            ],
+            "initialize\n",
+        ),
+        (
+            ["-f", "{.id}"],
+            [
+                dict(jsonrpc="2.0", id=1, method="initialize", params=dict()),
+                dict(jsonrpc="2.0", id=1, result=dict()),
+            ],
+            "1\n1\n",
+        ),
+    ],
+)
+def test_file_output(
+    tmp_path: pathlib.Path,
+    record: argparse.ArgumentParser,
+    logger: logging.Logger,
+    args: List[str],
+    messages: List[Dict[str, Any]],
+    expected: str,
+):
+    """Ensure that we can log to files correctly.
+
+    Parameters
+    ----------
+    tmp_path
+       pytest's ``tmp_path`` fixture
+
+    record
+       The record command's cli parser
+
+    logger
+       The logging instance to use
+
+    messages
+       The messages to record
+
+    expected
+       The expected file output.
+    """
+    log = tmp_path / "log.json"
+    parsed_args = record.parse_args(["record", "--to-file", str(log), *args])
+
+    setup_file_output(parsed_args, logger)
+
+    for message in messages:
+        logger.info("%s", message, extra={"source": "client"})
+
+    assert log.read_text() == expected