diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3d1dd95..5c73616 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -48,13 +48,14 @@ releases may contain breaking changes.
   against the most recent `save()`.
 - LIFT-folder handling: `RangesFile` (standalone `.lift-ranges` documents,
   same fidelity guarantees), automatic companion discovery/tracking on load
-  (`Lexicon.ranges_files`), `save()` writes companions together,
-  `all_ranges()` merged view, `media_refs()` / `missing_media()` helpers,
-  build-from-scratch helpers `Lexicon.add_ranges_file()` /
-  `RangesFile.add_range()` / `Range.add_element()` (`save()` writes and
-  header-references a new companion beside the `.lift`); vendored
-  `schemas/lift-ranges-0.13.rng` — the first schema for standalone
-  ranges documents.
+  (`Lexicon.ranges_files`, resolving a companion whose filename differs from
+  the `.lift` only in case, as Windows-authored folders often do), `save()`
+  writes companions together, `all_ranges()` merged view, `media_refs()` /
+  `missing_media()` helpers, build-from-scratch helpers
+  `Lexicon.add_ranges_file()` / `RangesFile.add_range()` /
+  `Range.add_element()` (`save()` writes and header-references a new companion
+  beside the `.lift`); vendored `schemas/lift-ranges-0.13.rng` — the first
+  schema for standalone ranges documents.
 - Zipped LIFT packages: `sil_lift.load()` reads a `.zip` (both the flat and
   folder-wrapped layouts, junk entries like `__MACOSX` ignored),
   `Lexicon.save_zip()` writes one (carrying media, `WritingSystems/`, and other
diff --git a/src/sil_lift/_model.py b/src/sil_lift/_model.py
index e130f9f..2bde198 100644
--- a/src/sil_lift/_model.py
+++ b/src/sil_lift/_model.py
@@ -452,6 +452,38 @@ def _normalize_href(href: str) -> Path | None:
     return Path(normalized)
 
 
+def _existing_file(candidate: Path, listings: dict[Path, dict[str, Path]]) -> Path | None:
+    """``candidate`` if it is a file, else one whose name differs only in case.
+
+    LIFT folders are written on Windows, where the filesystem folds case, and
+    read everywhere. A folder whose ``.lift`` and ``.lift-ranges`` disagree in
+    case (``Dict.LIFT`` beside ``Dict.lift-ranges``) resolves there and, before
+    this fallback, silently did not on a case-sensitive filesystem.
+
+    The fallback runs only where the exact name matched no file, so a
+    case-folding filesystem never reaches it and nothing changes there. Where
+    several names fold together, the lexicographically first wins — arbitrary,
+    but stable across runs, which "whatever the directory yields first" would
+    not be. ``listings`` caches one directory read per folder.
+    """
+    try:
+        if candidate.is_file():
+            return candidate
+    except OSError:
+        return None
+    folder = candidate.parent
+    if folder not in listings:
+        files: dict[str, Path] = {}
+        try:
+            for path in sorted(folder.iterdir()):
+                if path.is_file():
+                    files.setdefault(path.name.lower(), path)
+        except OSError:
+            pass  # unreadable folder: no candidate resolves out of it
+        listings[folder] = files
+    return listings[folder].get(candidate.name.lower())
+
+
 def _same_dir(left: Path, right: Path | None) -> bool:
     """Whether two paths denote the same directory, spelling aside.
 
@@ -510,7 +542,10 @@ def load(cls, path: str | os.PathLike[str], *, resolve_ranges: bool = True) -> L
         ``range/@href`` both the href resolved as a path relative to the
         ``.lift`` file and its bare basename in the same directory (FLEx
         hrefs are usually dangling absolute ``file://C:/...`` paths from the
-        exporting machine, so the basename is what resolves locally).
+        exporting machine, so the basename is what resolves locally). A
+        candidate that no file matches exactly still resolves to a file whose
+        name differs only in case, so a folder authored on Windows loads the
+        same way on a case-sensitive filesystem.
 
         A ``.zip`` path is treated as a packaged LIFT folder: it is extracted
         to a temporary directory (kept alive for the returned lexicon's
@@ -544,14 +579,17 @@ def _resolve_ranges(self) -> None:
             basename = range_.href.replace("\\", "/").rpartition("/")[2]
             if basename:
                 candidates.append(base / basename)
+        listings: dict[Path, dict[str, Path]] = {}
         for candidate in candidates:
+            found = _existing_file(candidate, listings)
+            if found is None:
+                continue
             try:
-                resolved = candidate.resolve()
-                exists = candidate.is_file()
+                resolved = found.resolve()
             except OSError:
                 continue
-            if exists and resolved not in self.ranges_files:
-                self.ranges_files[resolved] = RangesFile.load(candidate)
+            if resolved not in self.ranges_files:
+                self.ranges_files[resolved] = RangesFile.load(found)
 
     def save(self, path: str | os.PathLike[str] | None = None) -> None:
         """Write the ``.lift`` file and every tracked ``.lift-ranges`` companion.
diff --git a/tests/test_ranges_folder.py b/tests/test_ranges_folder.py
index 9544db9..4869bc2 100644
--- a/tests/test_ranges_folder.py
+++ b/tests/test_ranges_folder.py
@@ -225,6 +225,55 @@ def test_missing_media_flags_broken_ref(tmp_path: Path) -> None:
     assert [r.href for r in missing] == ["pictures\\sdd.png"]
 
 
+def _write_case_variant_pair(folder: Path, lift_name: str, ranges_name: str) -> Path:
+    """A loadable .lift plus companion under arbitrary filename casing.
+
+    Deliberately not named after the fixture, so the header's ``range/@href``
+    basename candidate finds nothing — only the sibling candidate resolves these.
+    """
+    folder.mkdir(parents=True, exist_ok=True)
+    (folder / lift_name).write_bytes((PAIR_DIR / "test20080407.lift").read_bytes())
+    (folder / ranges_name).write_bytes((PAIR_DIR / "test20080407.lift-ranges").read_bytes())
+    return folder / lift_name
+
+
+def _case_sensitive_filesystem(folder: Path) -> bool:
+    (folder / "CaseProbe").mkdir()
+    return not (folder / "caseprobe").exists()
+
+
+def test_companion_resolves_when_lift_suffix_is_uppercase(tmp_path: Path) -> None:
+    lift = _write_case_variant_pair(tmp_path / "pkg", "Dict.LIFT", "Dict.lift-ranges")
+    lexicon = sil_lift.load(lift)
+    assert lexicon.all_ranges()["grammatical-info"].elements
+
+
+def test_companion_resolves_when_companion_suffix_is_uppercase(tmp_path: Path) -> None:
+    lift = _write_case_variant_pair(tmp_path / "pkg", "Dict.lift", "Dict.LIFT-RANGES")
+    lexicon = sil_lift.load(lift)
+    assert lexicon.all_ranges()["grammatical-info"].elements
+
+
+def test_case_folded_companions_resolve_deterministically(tmp_path: Path) -> None:
+    if not _case_sensitive_filesystem(tmp_path):
+        pytest.skip("needs a case-sensitive filesystem to hold both spellings at once")
+    # Neither spelling matches the Dict.LIFT-ranges candidate exactly, so the
+    # tie-break picks one: lexicographically first, the same one every run.
+    folder = tmp_path / "pkg"
+    lift = _write_case_variant_pair(folder, "Dict.LIFT", "Dict.lift-ranges")
+    (folder / "Dict.Lift-ranges").write_bytes((folder / "Dict.lift-ranges").read_bytes())
+    lexicon = sil_lift.load(lift)
+    assert [path.name for path in lexicon.ranges_files] == ["Dict.Lift-ranges"]
+
+
+def test_absent_companion_stays_absent(tmp_path: Path) -> None:
+    # The fallback must not look outside the folder for a name not in it.
+    folder = tmp_path / "pkg"
+    folder.mkdir()
+    (folder / "Dict.lift").write_bytes((PAIR_DIR / "test20080407.lift").read_bytes())
+    assert sil_lift.load(folder / "Dict.lift").ranges_files == {}
+
+
 @pytest.mark.parametrize(
     ("href", "expected"),
     [