diff --git a/nominatim/tokenizer/factory.py b/nominatim/tokenizer/factory.py
index e0c06293..069672d4 100644
--- a/nominatim/tokenizer/factory.py
+++ b/nominatim/tokenizer/factory.py
@@ -15,6 +15,7 @@ normalizer module is installed, when the tokenizer is created.
 """
 import logging
 import importlib
+from pathlib import Path
 
 from ..errors import UsageError
 from ..db import properties
@@ -25,12 +26,13 @@ LOG = logging.getLogger()
 def _import_tokenizer(name):
     """ Load the tokenizer.py module from project directory.
     """
-    try:
-        return importlib.import_module('nominatim.tokenizer.' + name + '_tokenizer')
-    except ModuleNotFoundError as exp:
+    src_file = Path(__file__).parent / (name + '_tokenizer.py')
+    if not src_file.is_file():
         LOG.fatal("No tokenizer named '%s' available. "
                   "Check the setting of NOMINATIM_TOKENIZER.", name)
-        raise UsageError('Tokenizer not found') from exp
+        raise UsageError('Tokenizer not found')
+
+    return importlib.import_module('nominatim.tokenizer.' + name + '_tokenizer')
 
 
 def create_tokenizer(config, init_db=True, module_name=None):
diff --git a/test/python/conftest.py b/test/python/conftest.py
index 923e6876..a3249474 100644
--- a/test/python/conftest.py
+++ b/test/python/conftest.py
@@ -17,6 +17,7 @@ from nominatim.config import Configuration
 from nominatim.db import connection
 from nominatim.db.sql_preprocessor import SQLPreprocessor
 from nominatim.db import properties
+import nominatim.tokenizer.factory
 
 import dummy_tokenizer
 import mocks
@@ -273,7 +274,7 @@ def tokenizer_mock(monkeypatch, property_table, temp_db_conn, tmp_path):
     def _import_dummy(module, *args, **kwargs):
         return dummy_tokenizer
 
-    monkeypatch.setattr(importlib, "import_module", _import_dummy)
+    monkeypatch.setattr(nominatim.tokenizer.factory, "_import_tokenizer", _import_dummy)
     properties.set_property(temp_db_conn, 'tokenizer', 'dummy')
 
     def _create_tokenizer():