diff --git a/tlfi/__main__.py b/tlfi/__main__.py
index b7c6346..a704a58 100644
--- a/tlfi/__main__.py
+++ b/tlfi/__main__.py
@@ -10,6 +10,8 @@ import difflib
 import gzip
 import re
 import unicodedata
+from functools import cache
+from os import environ
 from pathlib import Path
 
 from bs4 import BeautifulSoup, NavigableString
@@ -27,9 +29,11 @@ except ImportError:
 def main():
     ap = argparse.ArgumentParser(description="TLFi CLI")
     ap.add_argument("query", help="mot(s) à chercher")
-    ap.add_argument("-f", "--lexical-forms", default="lexical_forms.txt",
+    ap.add_argument("-f", "--lexical-forms",
+                    default=get_root_path() / "lexical_forms.txt",
                     help="fichier des formes lexicales")
-    ap.add_argument("-d", "--definitions", default="definitions",
+    ap.add_argument("-d", "--definitions",
+                    default=get_root_path() / "definitions",
                     help="répertoire des définitions")
     args = ap.parse_args()
 
@@ -42,6 +46,11 @@ def main():
             show_definition(d)
 
 
+@cache
+def get_root_path():
+    return Path(environ.get("TLFI_ROOT", "."))
+
+
 def lookup(query, lexical_forms_path):
     """Return a form for which a definition might exist, else None.
 
@@ -63,7 +72,7 @@ def lookup(query, lexical_forms_path):
     return None
 
 
-def get_definition_paths(query, definitions):
+def get_definition_paths(query, definitions) -> list:
     """Return a list of definition file paths for this lexical form."""
     nfkd = unicodedata.normalize("NFKD", query[0])
     first_char = next((c for c in nfkd if not unicodedata.combining(c)), "")
@@ -90,7 +99,7 @@ def show_definition(def_path):
 TAG_STRIP_RE = re.compile(r"\s+")
 
 
-def parse_tag(tag):
+def parse_tag(tag) -> str:
     if isinstance(tag, NavigableString):
         return TAG_STRIP_RE.sub(" ", tag)
     content = ""