diff --git a/xhu.py b/xhu.py
index a28c5a8..b999957 100644
--- a/xhu.py
+++ b/xhu.py
@@ -29,6 +29,7 @@ import pathlib
 import typing
 
 import flask
+import werkzeug.exceptions
 
 app = flask.Flask("xmpp-http-upload")
 app.config.from_envvar("XMPP_HTTP_UPLOAD_CONFIG")
@@ -39,16 +40,11 @@ if app.config['ENABLE_CORS']:
     CORS(app)
 
 
-def sanitized_join(path: str, root: pathlib.Path) -> pathlib.Path:
-    result = (root / path).absolute()
-    if not str(result).startswith(str(root) + "/"):
-        raise ValueError("resulting path is outside root")
-    return result
-
-
-def get_paths(base_path: pathlib.Path):
-    data_file = pathlib.Path(str(base_path) + ".data")
-    metadata_file = pathlib.Path(str(base_path) + ".meta")
+def get_paths(root: str, sub_path: str) \
+        -> typing.Tuple[pathlib.Path, pathlib.Path]:
+    base_path = flask.safe_join(root, sub_path)
+    data_file = pathlib.Path(base_path + ".data")
+    metadata_file = pathlib.Path(base_path + ".meta")
 
     return data_file, metadata_file
 
@@ -58,15 +54,10 @@ def load_metadata(metadata_file):
         return json.load(f)
 
 
-def get_info(path: str, root: pathlib.Path) -> typing.Tuple[
+def get_info(path: str) -> typing.Tuple[
         pathlib.Path,
         dict]:
-    dest_path = sanitized_join(
-        path,
-        pathlib.Path(app.config["DATA_ROOT"]),
-    )
-
-    data_file, metadata_file = get_paths(dest_path)
+    data_file, metadata_file = get_paths(app.config["DATA_ROOT"], path)
 
     return data_file, load_metadata(metadata_file)
 
@@ -104,11 +95,8 @@ def stream_file(src, dest, nbytes):
 @app.route("/<path:path>", methods=["PUT"])
 def put_file(path):
     try:
-        dest_path = sanitized_join(
-            path,
-            pathlib.Path(app.config["DATA_ROOT"]),
-        )
-    except ValueError:
+        data_file, metadata_file = get_paths(app.config["DATA_ROOT"], path)
+    except werkzeug.exceptions.NotFound:
         return flask.Response(
             "Not Found",
             404,
@@ -134,8 +122,7 @@ def put_file(path):
         "application/octet-stream",
     )
 
-    dest_path.parent.mkdir(parents=True, exist_ok=True, mode=0o770)
-    data_file, metadata_file = get_paths(dest_path)
+    data_file.parent.mkdir(parents=True, exist_ok=True, mode=0o770)
 
     try:
         with write_file(data_file) as fout:
@@ -189,13 +176,10 @@ def generate_headers(response_headers, metadata_headers):
 @app.route("/<path:path>", methods=["HEAD"])
 def head_file(path):
     try:
-        data_file, metadata = get_info(
-            path,
-            pathlib.Path(app.config["DATA_ROOT"])
-        )
+        data_file, metadata = get_info(path)
 
         stat = data_file.stat()
-    except (OSError, ValueError):
+    except (OSError, werkzeug.exceptions.NotFound):
         return flask.Response(
             "Not Found",
             404,
@@ -214,11 +198,8 @@ def head_file(path):
 @app.route("/<path:path>", methods=["GET"])
 def get_file(path):
     try:
-        data_file, metadata = get_info(
-            path,
-            pathlib.Path(app.config["DATA_ROOT"])
-        )
-    except (OSError, ValueError):
+        data_file, metadata = get_info(path)
+    except (OSError, werkzeug.exceptions.NotFound):
         return flask.Response(
             "Not Found",
             404,