diff --git a/radicale/log.py b/radicale/log.py
index 49143457..64304c1f 100644
--- a/radicale/log.py
+++ b/radicale/log.py
@@ -26,6 +26,7 @@ Log messages are sent to the first available target of:
 """
 
 import contextlib
+import io
 import logging
 import os
 import socket
@@ -33,8 +34,8 @@ import struct
 import sys
 import threading
 import time
-from typing import (Any, Callable, ClassVar, Dict, Iterator, Optional, Tuple,
-                    Union)
+from typing import (Any, Callable, ClassVar, Dict, Iterator, Mapping, Optional,
+                    Tuple, Union, cast)
 
 from radicale import types
 
@@ -85,6 +86,7 @@ class ThreadedStreamHandler(logging.Handler):
     _streams: Dict[int, types.ErrorStream]
     _journal_stream_id: Optional[Tuple[int, int]]
     _journal_socket: Optional[socket.socket]
+    _journal_socket_failed: bool
 
     def __init__(self) -> None:
         super().__init__()
@@ -92,42 +94,52 @@ class ThreadedStreamHandler(logging.Handler):
         self._journal_stream_id = None
         with contextlib.suppress(TypeError, ValueError):
             dev, inode = os.environ.get("JOURNAL_STREAM", "").split(":", 1)
-            self._journal_stream_id = int(dev), int(inode)
+            self._journal_stream_id = (int(dev), int(inode))
         self._journal_socket = None
-        if self._journal_stream_id and hasattr(socket, "AF_UNIX"):
-            journal_socket = socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM)
-            try:
-                journal_socket.connect("/run/systemd/journal/socket")
-            except OSError:
-                journal_socket.close()
-            else:
-                self._journal_socket = journal_socket
+        self._journal_socket_failed = False
 
-    def _detect_journal(self, stream):
-        if not self._journal_stream_id:
+    def _detect_journal(self, stream: types.ErrorStream) -> bool:
+        if not self._journal_stream_id or not isinstance(stream, io.IOBase):
             return False
         try:
             stat = os.fstat(stream.fileno())
-        except Exception:
+        except OSError:
             return False
         return self._journal_stream_id == (stat.st_dev, stat.st_ino)
 
     @staticmethod
-    def _encode_journal(data):
+    def _encode_journal(data: Mapping[str, Optional[Union[str, int]]]
+                        ) -> bytes:
         msg = b""
         for key, value in data.items():
             if value is None:
                 continue
-            key = key.encode()
-            value = str(value).encode()
-            if b"\n" in value:
-                msg += (key + b"\n" +
-                        struct.pack("<Q", len(value)) + value + b"\n")
+            keyb = key.encode()
+            valueb = str(value).encode()
+            if b"\n" in valueb:
+                msg += (keyb + b"\n" +
+                        struct.pack("<Q", len(valueb)) + valueb + b"\n")
             else:
-                msg += key + b"=" + value + b"\n"
+                msg += keyb + b"=" + valueb + b"\n"
         return msg
 
-    def _emit_journal(self, record):
+    def _try_emit_journal(self, record: logging.LogRecord) -> bool:
+        if not self._journal_socket:
+            # Try to connect to systemd journal socket
+            if self._journal_socket_failed or not hasattr(socket, "AF_UNIX"):
+                return False
+            journal_socket = None
+            try:
+                journal_socket = socket.socket(
+                    socket.AF_UNIX, socket.SOCK_DGRAM)
+                journal_socket.connect("/run/systemd/journal/socket")
+            except OSError:
+                self._journal_socket_failed = True
+                if journal_socket:
+                    journal_socket.close()
+                return False
+            self._journal_socket = journal_socket
+
         priority = {"DEBUG": 7,
                     "INFO": 6,
                     "WARNING": 4,
@@ -136,7 +148,7 @@ class ThreadedStreamHandler(logging.Handler):
         timestamp = time.strftime("%Y-%m-%dT%H:%M:%S.%%03dZ",
                                   time.gmtime(record.created)) % record.msecs
         data = {"PRIORITY": priority,
-                "TID": record.tid,
+                "TID": cast(Optional[int], getattr(record, "tid", None)),
                 "SYSLOG_IDENTIFIER": record.name,
                 "SYSLOG_FACILITY": 1,
                 "SYSLOG_PID": record.process,
@@ -146,12 +158,12 @@ class ThreadedStreamHandler(logging.Handler):
                 "CODE_FUNC": record.funcName,
                 "MESSAGE": self.format(record)}
         self._journal_socket.sendall(self._encode_journal(data))
+        return True
 
     def emit(self, record: logging.LogRecord) -> None:
         try:
             stream = self._streams.get(threading.get_ident(), sys.stderr)
-            if self._journal_socket and self._detect_journal(stream):
-                self._emit_journal(record)
+            if self._detect_journal(stream) and self._try_emit_journal(record):
                 return
             msg = self.format(record)
             stream.write(msg)
diff --git a/radicale/types.py b/radicale/types.py
index 0eb3fd6a..c7e1904a 100644
--- a/radicale/types.py
+++ b/radicale/types.py
@@ -50,8 +50,8 @@ if sys.version_info >= (3, 8):
 
     @runtime_checkable
     class ErrorStream(Protocol):
-        def flush(self) -> None: ...
-        def write(self, s: str) -> None: ...
+        def flush(self) -> object: ...
+        def write(self, s: str) -> object: ...
 else:
     ErrorStream = Any
     InputStream = Any