diff --git a/src/pendulum/tz/local_timezone.py b/src/pendulum/tz/local_timezone.py
index 9418b05d..5549a7e3 100644
--- a/src/pendulum/tz/local_timezone.py
+++ b/src/pendulum/tz/local_timezone.py
@@ -215,7 +215,9 @@ def _get_unix_timezone(_root: str = "/") -> Timezone:
         tzpath = Path(_root) / filename
         if tzpath.is_file():
             with tzpath.open("rb") as f:
-                return Timezone.from_file(f)
+                tz = Timezone.from_file(f)
+                if tz.key is not None:
+                    return tz
 
     warnings.warn(
         "Unable not find any timezone configuration, defaulting to UTC.", stacklevel=1
@@ -231,7 +233,7 @@ def _tz_from_env(tzenv: str) -> Timezone:
     # TZ specifies a file
     if os.path.isfile(tzenv):
         with open(tzenv, "rb") as f:
-            return Timezone.from_file(f)
+            return Timezone.from_file(f, key=tzenv)
 
     # TZ specifies a zoneinfo zone.
     try:
diff --git a/tests/tz/test_local_timezone.py b/tests/tz/test_local_timezone.py
index b8eff6de..09b22a7c 100644
--- a/tests/tz/test_local_timezone.py
+++ b/tests/tz/test_local_timezone.py
@@ -50,3 +50,27 @@ def test_unix_etc_timezone_dir():
     tz = _get_unix_timezone(_root=root_path)
 
     assert tz.name == "Europe/Paris"
+
+
+@pytest.mark.skipif(
+    sys.platform == "win32", reason="Test only available for UNIX systems"
+)
+def test_unix_localtime_regular_file_defaults_to_utc():
+    # /etc/localtime as a bare copy of a zoneinfo file (no IANA key), as
+    # found in minimal containers / Slurm jobs, used to yield a Timezone
+    # with key=None, which crashed the Rust helpers (#989). It must now
+    # fall through to the UTC default with a named key.
+    import shutil
+    import tempfile
+
+    local_path = os.path.join(os.path.split(__file__)[0], "..")
+    root_path = tempfile.mkdtemp()
+    os.makedirs(os.path.join(root_path, "etc"), exist_ok=True)
+    shutil.copy(
+        os.path.join(local_path, "fixtures", "tz", "Paris"),
+        os.path.join(root_path, "etc", "localtime"),
+    )
+    tz = _get_unix_timezone(_root=root_path)
+
+    assert tz.key is not None
+    assert tz.name == "UTC"
diff --git a/tests/tz/test_timezone.py b/tests/tz/test_timezone.py
index 6ce475d3..a8f88b72 100644
--- a/tests/tz/test_timezone.py
+++ b/tests/tz/test_timezone.py
@@ -487,7 +487,10 @@ def _paris_tzif_bytes() -> bytes:
 
 
 def test_from_file_without_a_key_can_be_pickled():
-    # get_local_timezone()'s last-resort fallback builds a Timezone this same way, with no key.
+    # Timezone.from_file without a key yields a keyless Timezone (key is
+    # None); this is still supported for pickling / utcoffset (#989). The
+    # local-timezone resolver no longer returns such a value, defaulting
+    # to UTC instead (see test_unix_localtime_regular_file_defaults_to_utc).
     from io import BytesIO
 
     import pendulum.tz.timezone as timezone_module