2 files changed, 9 insertions, 5 deletions
diff --git a/pint/delegates/txt_defparser/context.py b/pint/delegates/txt_defparser/context.py
index 6be5171..5ede7b4 100644
--- a/pint/delegates/txt_defparser/context.py
+++ b/pint/delegates/txt_defparser/context.py
@@ -19,6 +19,7 @@ from __future__ import annotations
 import numbers
 import re
 import typing as ty
+from typing import Optional, Union
 from dataclasses import dataclass
 
 from ..._vendor import flexparser as fp
@@ -27,12 +28,12 @@ from ..base_defparser import ParserConfig, PintParsedStatement
 from . import block, common, plain
 
 # TODO check syntax
-T = ty.TypeVar("T", bound="ForwardRelation | BidirectionalRelation")
+T = ty.TypeVar("T", bound="Union[ForwardRelation, BidirectionalRelation]")
 
 
 def _from_string_and_context_sep(
     cls: type[T], s: str, config: ParserConfig, separator: str
-) -> T | None:
+) -> Optional[T]:
     if separator not in s:
         return None
     if ":" not in s:
@@ -199,7 +200,7 @@ class ContextDefinition(
         return self.opening.defaults
 
     @property
-    def relations(self) -> tuple[BidirectionalRelation | ForwardRelation, ...]:
+    def relations(self) -> tuple[Union[BidirectionalRelation, ForwardRelation], ...]:
         return tuple(
             r
             for r in self.body
diff --git a/pint/delegates/txt_defparser/defparser.py b/pint/delegates/txt_defparser/defparser.py
index 16f5a94..a5ccb08 100644
--- a/pint/delegates/txt_defparser/defparser.py
+++ b/pint/delegates/txt_defparser/defparser.py
@@ -2,6 +2,7 @@ from __future__ import annotations
 
 import pathlib
 import typing as ty
+from typing import Optional, Union
 
 from ..._vendor import flexcache as fc
 from ..._vendor import flexparser as fp
@@ -130,7 +131,9 @@ class DefParser:
             else:
                 yield stmt
 
-    def parse_file(self, filename: pathlib.Path | str, cfg: ParserConfig | None = None):
+    def parse_file(
+        self, filename: Union[pathlib.Path, str], cfg: Optional[ParserConfig] = None
+    ):
         return fp.parse(
             filename,
             _PintParser,
@@ -138,7 +141,7 @@ class DefParser:
             diskcache=self._diskcache,
         )
 
-    def parse_string(self, content: str, cfg: ParserConfig | None = None):
+    def parse_string(self, content: str, cfg: Optional[ParserConfig] = None):
         return fp.parse_bytes(
             content.encode("utf-8"),
             _PintParser,