diff --git a/packaging/markers.py b/packaging/markers.py
index 1d61adaff..03d8cdefc 100644
--- a/packaging/markers.py
+++ b/packaging/markers.py
@@ -5,7 +5,6 @@
 import operator
 import os
 import platform
-import re
 import sys
 from typing import Any, Callable, Dict, List, Optional, Tuple, Union
 
@@ -22,6 +21,7 @@
 )
 
 from .specifiers import InvalidSpecifier, Specifier
+from .utils import canonicalize_name
 
 __all__ = [
     "InvalidMarker",
@@ -223,8 +223,10 @@ def _get_env(environment: Dict[str, str], name: str) -> str:
 def _normalize(*values: str, key: str) -> Tuple[str, ...]:
     # PEP 685 – Comparison of extra names for optional distribution dependencies
     # https://peps.python.org/pep-0685/
+    # > When comparing extra names, tools MUST normalize the names being
+    # > compared using the semantics outlined in PEP 503 for names
     if key == "extra":
-        return tuple(re.sub(r"[-_.]+", "-", v).lower() for v in values)
+        return tuple(canonicalize_name(v) for v in values)
 
     # other environment markes don't have such standards
     return values