diff --git a/swh/loader/package/loader.py b/swh/loader/package/loader.py
--- a/swh/loader/package/loader.py
+++ b/swh/loader/package/loader.py
@@ -27,7 +27,7 @@
 import attr
 import sentry_sdk
 
-from swh.core.config import SWHConfig
+from swh.core.config import load_from_envvar
 from swh.core.tarball import uncompress
 from swh.loader.package.utils import download
 from swh.model import from_disk
@@ -117,15 +117,17 @@
 TPackageInfo = TypeVar("TPackageInfo", bound=BasePackageInfo)
 
 
+DEFAULT_CONFIG = {
+    "max_content_size": 100 * 1024 * 1024,
+    "create_authorities": True,
+    "create_fetchers": True,
+}
+
+
 class PackageLoader(Generic[TPackageInfo]):
     # Origin visit type (str) set by the loader
     visit_type = ""
 
-    DEFAULT_CONFIG = {
-        "create_authorities": ("bool", True),
-        "create_fetchers": ("bool", True),
-    }
-
     def __init__(self, url):
         """Loader's constructor. This raises exception if the minimal required
            configuration is missing (cf. fn:`check` method).
@@ -135,7 +137,7 @@
 
         """
         # This expects to use the environment variable SWH_CONFIG_FILENAME
-        self.config = SWHConfig.parse_config_file()
+        self.config = load_from_envvar(DEFAULT_CONFIG)
         self._check_configuration()
         self.storage: StorageInterface = get_storage(**self.config["storage"])
         self.url = url
diff --git a/swh/loader/package/pypi/tests/test_pypi.py b/swh/loader/package/pypi/tests/test_pypi.py
--- a/swh/loader/package/pypi/tests/test_pypi.py
+++ b/swh/loader/package/pypi/tests/test_pypi.py
@@ -3,11 +3,13 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
+import copy
 import os
 from os import path
 from unittest.mock import patch
 
 import pytest
+import yaml
 
 from swh.core.pytest_plugin import requests_mock_datadir_factory
 from swh.core.tarball import uncompress
@@ -143,13 +145,25 @@
 # configuration error #
 
 
-def test_badly_configured_loader_raise(monkeypatch):
-    """Badly configured loader should raise"""
+def test_no_env_swh_config_filename_raise(monkeypatch):
+    """No SWH_CONFIG_FILENAME environment variable makes init raise"""
     monkeypatch.delenv("SWH_CONFIG_FILENAME", raising=False)
-    with pytest.raises(ValueError) as e:
+    with pytest.raises(AssertionError, match="environment variable is undefined"):
         PyPILoader(url="some-url")
 
-    assert "Misconfiguration" in e.value.args[0]
+
+def test_badly_configured_loader_raise(tmp_path, swh_loader_config, monkeypatch):
+    """Badly configured loader should raise"""
+    wrong_config = copy.deepcopy(swh_loader_config)
+    wrong_config.pop("storage")
+
+    conf_path = os.path.join(str(tmp_path), "loader.yml")
+    with open(conf_path, "w") as f:
+        f.write(yaml.dump(wrong_config))
+    monkeypatch.setenv("SWH_CONFIG_FILENAME", conf_path)
+
+    with pytest.raises(ValueError, match="Misconfiguration"):
+        PyPILoader(url="some-url")
 
 
 def test_pypi_api_url():