diff --git a/src/sshkeyboard/__init__.py b/src/sshkeyboard/__init__.py
index f203fb1..29fd65d 100644
--- a/src/sshkeyboard/__init__.py
+++ b/src/sshkeyboard/__init__.py
@@ -12,7 +12,7 @@
 from platform import system
 from time import time
 from types import SimpleNamespace
-from typing import Any, Callable, Optional
+from typing import Any, Callable, Generator, Optional, TextIO, Tuple
 
 try:
     from ._asyncio_run_backport_36 import run36
@@ -166,7 +166,6 @@ def listen_keyboard(
     max_thread_pool_workers: Optional[int] = None,
     sleep: float = 0.01,
 ) -> None:
-
     """Listen for keyboard events and fire `on_press` and `on_release` callback
     functions
 
@@ -380,11 +379,14 @@ def press(key):
         _should_run = False
 
 
-def _is_python_36():
+def _is_python_36() -> bool:
     return sys.version_info.major == 3 and sys.version_info.minor == 6
 
 
-def _check_callback_ok(function, name):
+def _check_callback_ok(
+    function: Optional[Callable[[str], Any]],
+    name: str,
+) -> None:
     if function is not None:
         assert callable(function), f"{name} must be None or callable"
         assert _takes_at_least_one_param(
@@ -396,12 +398,12 @@ def _check_callback_ok(function, name):
         )
 
 
-def _takes_at_least_one_param(function):
+def _takes_at_least_one_param(function: Callable[[str], Any]) -> bool:
     sig = signature(function)
     return len(sig.parameters.values()) >= 1
 
 
-def _default_empty_params(function):
+def _default_empty_params(function: Callable[[str], Any]) -> Tuple[str, ...]:
     sig = signature(function)
     return tuple(
         param.name
@@ -413,20 +415,25 @@ def _default_empty_params(function):
     )
 
 
-def _max_one_param_without_default(function):
+def _max_one_param_without_default(function: Callable[[str], Any]) -> bool:
     default_empty_params = _default_empty_params(function)
     return len(default_empty_params) <= 1
 
 
-def _done(task):
-    if not task.cancelled() and task.exception() is not None:
+def _done(task: asyncio.Task[Any] | concurrent.futures.Future[Any]) -> None:
+    if not task.cancelled():
         ex = task.exception()
-        traceback.print_exception(type(ex), ex, ex.__traceback__)
-        global _should_run
-        _should_run = False
+        if ex is not None:
+            traceback.print_exception(type(ex), ex, ex.__traceback__)
+            global _should_run
+            _should_run = False
 
 
-def _callback(cb_function, sequential, executor):
+def _callback(
+    cb_function: Optional[Callable[[str], Any]],
+    sequential: bool,
+    executor: Optional[concurrent.futures.Executor],
+):
     async def _cb(key):
         if cb_function is None:
             return
@@ -440,7 +447,7 @@ async def _cb(key):
             if asyncio.iscoroutinefunction(cb_function):
                 task = asyncio.create_task(cb_function(key))
                 task.add_done_callback(_done)
-            else:
+            elif executor is not None:
                 future = executor.submit(cb_function, key)
                 future.add_done_callback(_done)
 
@@ -450,7 +457,7 @@ async def _cb(key):
 # Raw and _nonblocking inspiration from:
 # http://ballingt.com/_nonblocking-stdin-in-python-3/
 @contextmanager
-def _raw(stream):
+def _raw(stream: TextIO) -> Generator[None, None, None]:
     # Not required on Windows
     if _is_windows:
         yield
@@ -465,7 +472,7 @@ def _raw(stream):
 
 
 @contextmanager
-def _nonblocking(stream):
+def _nonblocking(stream: TextIO) -> Generator[None, None, None]:
     # Not required on Windows
     if _is_windows:
         yield
@@ -480,14 +487,14 @@ def _nonblocking(stream):
         fcntl.fcntl(fd, fcntl.F_SETFL, orig_fl)
 
 
-def _read_char(debug):
+def _read_char(debug: bool) -> Optional[str]:
     if _is_windows:
         return _read_char_win(debug)
     else:
         return _read_char_unix(debug)
 
 
-def _read_char_win(debug):
+def _read_char_win(debug: bool) -> Optional[str]:
     # Return if nothing to read
     if not msvcrt.kbhit():
         return ""
@@ -512,7 +519,7 @@ def _read_char_win(debug):
     return char
 
 
-def _read_char_unix(debug):
+def _read_char_unix(debug: bool) -> Optional[str]:
     char = _read_unix_stdin(1)
 
     # Skip and continue if read failed
@@ -535,7 +542,7 @@ def _read_char_unix(debug):
     return char
 
 
-def _read_unix_stdin(amount):
+def _read_unix_stdin(amount: int) -> Optional[str]:
     try:
         return sys.stdin.read(amount)
     except IOError:
@@ -543,20 +550,24 @@ def _read_unix_stdin(amount):
 
 
 # '\x' at the start is a good indicator for ansi character
-def _is_unix_ansi(char):
+def _is_unix_ansi(char: str) -> bool:
     rep = repr(char)
     return len(rep) >= 2 and rep[1] == "\\" and rep[2] == "x"
 
 
-def _read_and_parse_unix_ansi(char):
-    char += _read_unix_stdin(5)
-    if char in _UNIX_ANSI_CHAR_TO_READABLE:
-        return _UNIX_ANSI_CHAR_TO_READABLE[char], char
-    else:
-        return None, char
+def _read_and_parse_unix_ansi(char: str) -> Tuple[Optional[str], str]:
+    extra = _read_unix_stdin(5)
+    if extra is not None:
+        char += extra
+        if char in _UNIX_ANSI_CHAR_TO_READABLE:
+            return _UNIX_ANSI_CHAR_TO_READABLE[char], char
+    return None, char
 
 
-async def _react_to_input(state, options):
+async def _react_to_input(
+    state: SimpleNamespace,
+    options: SimpleNamespace,
+) -> SimpleNamespace:
     # Read next character
     state.current = _read_char(options.debug)