diff --git a/jaxtyping/_typeguard/__init__.py b/jaxtyping/_typeguard/__init__.py
index da8d672..77d248c 100644
--- a/jaxtyping/_typeguard/__init__.py
+++ b/jaxtyping/_typeguard/__init__.py
@@ -14,7 +14,7 @@
 from inspect import Parameter, isclass, isfunction, isgeneratorfunction
 from io import BufferedIOBase, IOBase, RawIOBase, TextIOBase
 from traceback import extract_stack, print_stack
-from types import CodeType, FunctionType
+from types import CodeType, FunctionType, UnionType
 from typing import (
     IO, TYPE_CHECKING, AbstractSet, Any, AsyncIterable, AsyncIterator, BinaryIO, Callable, Dict,
     Generator, Iterable, Iterator, List, NewType, Optional, Sequence, Set, TextIO, Tuple, Type,
@@ -752,6 +752,10 @@ def check_type(argname: str, value, expected_type, memo: Optional[_TypeCheckMemo
 
     expected_type = resolve_forwardref(expected_type, memo)
     origin_type = getattr(expected_type, '__origin__', None)
+    # jaxtyping fix to typeguard, see https://github.com/patrick-kidger/jaxtyping/issues/73#issuecomment-3888576066
+    if isinstance(expected_type, UnionType):
+        origin_type = Union
+    # ~fix
     if origin_type is not None:
         checker_func = origin_type_checkers.get(origin_type)
         if checker_func:
diff --git a/test/test_pytree.py b/test/test_pytree.py
index cefc0ba..bfb2ea0 100644
--- a/test/test_pytree.py
+++ b/test/test_pytree.py
@@ -393,3 +393,15 @@ def test_pdoc():
         wl.pformat(PyTree[None | Callable[[PyTree[int, " T"]], str]], width=2).strip()
         == expected
     )
+
+
+# https://github.com/patrick-kidger/jaxtyping/issues/73#issuecomment-3888576066
+def test_new_union():
+    from jaxtyping._typeguard import typechecked
+
+    @typechecked
+    def f(x: int | bool):
+        pass
+
+    with pytest.raises(TypeError):
+        f(object())