diff --git a/problemtools/config.py b/problemtools/config.py
index 8cd470c9..a85493be 100644
--- a/problemtools/config.py
+++ b/problemtools/config.py
@@ -1,13 +1,15 @@
 import collections
 import os
 import yaml
+from pathlib import Path
+from typing import Mapping
 
 
 class ConfigError(Exception):
     pass
 
 
-def load_config(configuration_file):
+def load_config(configuration_file: str, priority_dirs: list[Path] = []) -> dict:
     """Load a problemtools configuration file.
 
     Args:
@@ -15,41 +17,42 @@ def load_config(configuration_file):
         relative to config directory so typically just a file name
         without paths, e.g. "languages.yaml".
     """
-    res = None
+    res: dict | None = None
 
-    for dirname in __config_file_paths():
-        path = os.path.join(dirname, configuration_file)
+    for dirname in __config_file_paths() + priority_dirs:
+        path = dirname / configuration_file
         new_config = None
-        if os.path.isfile(path):
+        if path.is_file():
             try:
                 with open(path, 'r') as config:
                     new_config = yaml.safe_load(config.read())
             except (yaml.parser.ParserError, yaml.scanner.ScannerError) as err:
-                raise ConfigError('Config file %s: failed to parse: %s' % (path, err))
+                raise ConfigError(f'Config file {path}: failed to parse: {err}')
         if res is None:
             if new_config is None:
-                raise ConfigError('Base configuration file %s not found in %s' % (configuration_file, path))
+                raise ConfigError(f'Base configuration file {configuration_file} not found in {path}')
             res = new_config
         elif new_config is not None:
             __update_dict(res, new_config)
 
+    assert res is not None, 'Failed to load config (should never happen, we should have hit an error in loop above)'
     return res
 
 
-def __config_file_paths():
+def __config_file_paths() -> list[Path]:
     """
     Paths in which to look for config files, by increasing order of
     priority (i.e., any config in the last path should take precedence
     over the others).
     """
     return [
-        os.path.join(os.path.dirname(__file__), 'config'),
-        os.path.join('/etc', 'kattis', 'problemtools'),
-        os.path.join(os.environ.get('XDG_CONFIG_HOME', os.path.join(os.path.expanduser('~'), '.config')), 'problemtools'),
+        Path(__file__).parent / 'config',
+        Path('/etc/kattis/problemtools'),
+        Path(os.environ.get('XDG_CONFIG_HOME', Path.home() / '.config')) / 'problemtools',
     ]
 
 
-def __update_dict(orig, update):
+def __update_dict(orig: dict, update: Mapping) -> None:
     """Deep update of a dictionary
 
     For each entry (k, v) in update such that both orig[k] and v are
diff --git a/problemtools/languages.py b/problemtools/languages.py
index 1bcb61f6..93941205 100644
--- a/problemtools/languages.py
+++ b/problemtools/languages.py
@@ -6,6 +6,7 @@
 import fnmatch
 import re
 import string
+from pathlib import Path
 
 from . import config
 
@@ -218,10 +219,10 @@ def update(self, data):
             priorities[lang.priority] = lang_id
 
 
-def load_language_config():
+def load_language_config(probdir_parent: Path) -> Languages:
     """Load language configuration.
 
     Returns:
         Languages object for the set of languages.
     """
-    return Languages(config.load_config('languages.yaml'))
+    return Languages(config.load_config('languages.yaml', [probdir_parent]))
diff --git a/problemtools/verifyproblem.py b/problemtools/verifyproblem.py
index 9005e34e..ef424af0 100644
--- a/problemtools/verifyproblem.py
+++ b/problemtools/verifyproblem.py
@@ -1902,7 +1902,7 @@ def __init__(self, probdir: str, args: argparse.Namespace):
         self.probdir = os.path.realpath(probdir)
         self.shortname: str = os.path.basename(self.probdir)
         super().__init__(self.shortname, self)
-        self.language_config = languages.load_language_config()
+        self.language_config = languages.load_language_config(Path(self.probdir).parent)
         self.testcase_by_infile: dict[str, TestCase] = {}
         self.loaded = False
         self._metadata: metadata.Metadata | None = None
diff --git a/tests/test_config.py b/tests/test_config.py
index 3307122d..35628a1b 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -5,9 +5,9 @@
 
 
 def config_paths_mock():
-    import os
+    from pathlib import Path
 
-    return [os.path.join(os.path.dirname(__file__), 'config1'), os.path.join(os.path.dirname(__file__), 'config2')]
+    return [Path(__file__).parent / 'config1', Path(__file__).parent / 'config2']
 
 
 def test_load_basic_config(monkeypatch):