diff --git a/tests/elab/treemap.lean b/tests/elab/treeMap2.lean
similarity index 100%
rename from tests/elab/treemap.lean
rename to tests/elab/treeMap2.lean
diff --git a/tests/lint.py b/tests/lint.py
index 7d3fae063bcf..25c02cf8f39d 100755
--- a/tests/lint.py
+++ b/tests/lint.py
@@ -190,5 +190,16 @@ def nag(reason: str, path: Path, fatal: bool = True) -> None:
         nag("has env_test.sh", file)
 
 
+# File confusion by case insensitive filesystems,
+# applies to entire repository
+
+seen: set[str] = set()
+for file in Path("..").glob("**/*"):
+    path = str(file).lower()
+    if path in seen:
+        nag("case sensitive", file)
+    seen.add(path)
+
+
 if ERROR:
     sys.exit(1)