diff --git a/pm/filesystem.py b/pm/filesystem.py
index 37d3e04de5..eb829818e3 100644
--- a/pm/filesystem.py
+++ b/pm/filesystem.py
@@ -7,6 +7,7 @@ from __future__ import annotations
 
 import errno
 import hashlib
+import ntpath
 import os
 from pathlib import Path
 import shutil
@@ -23,6 +24,37 @@ def is_junction(path: Path) -> bool:
     return os.name == "nt" and path.lstat().st_reparse_tag == stat.IO_REPARSE_TAG_MOUNT_POINT
 
 
+_VERBATIM = "\\\\?\\"
+_VERBATIM_UNC = "\\\\?\\UNC\\"
+
+
+def _long_form(text: str) -> str:
+    if text.startswith(_VERBATIM):
+        return text
+    # Windows stops normalising a verbatim path, so it must already be absolute,
+    # backslashed and free of `..` before the prefix goes on.
+    text = ntpath.abspath(text)
+    if text.startswith("\\\\"):
+        return _VERBATIM_UNC + text[2:]
+    return _VERBATIM + text
+
+
+def long_root(path: Path) -> Path:
+    """Spell a PM-owned root so Windows file calls beneath it are not cut at
+    MAX_PATH when LongPathsEnabled is 0 (the default). Every path joined onto the
+    result inherits the spelling; relative paths and digests are unchanged."""
+    return Path(_long_form(os.fspath(path))) if os.name == "nt" else path
+
+
+def native(path: str | os.PathLike[str]) -> str:
+    """The ordinary spelling, for text that leaves PM's own file calls: argv, cwd,
+    environment values, hashed identities, records and messages."""
+    text = os.fspath(path)
+    if text.startswith(_VERBATIM_UNC):
+        return "\\\\" + text[len(_VERBATIM_UNC):]
+    return text[len(_VERBATIM):] if text.startswith(_VERBATIM) else text
+
+
 def lock_fd(fd: int, *, wait: bool, timeout: float | None = None) -> bool:
     """Take the byte lock; ``timeout`` bounds the retry loop (None waits forever, 0 tries once)."""
     deadline = None if timeout is None else time.monotonic() + timeout
diff --git a/pm/store.py b/pm/store.py
index b6754651e6..ac0d63ce52 100644
--- a/pm/store.py
+++ b/pm/store.py
@@ -14,7 +14,7 @@ from contextlib import contextmanager
 from pathlib import Path
 from typing import IO
 
-from pm.filesystem import is_junction, retry_held
+from pm.filesystem import is_junction, long_root, retry_held
 
 
 
@@ -348,7 +348,7 @@ class Store:
     Hash-keyed archives survive failed installs. Publication releases them."""
 
     def __init__(self, root: Path):
-        self.root = root
+        self.root = long_root(root)
 
     def entry(self, name: str) -> Path:
         return self.root / name