diff --git a/swh/search/elasticsearch.py b/swh/search/elasticsearch.py
--- a/swh/search/elasticsearch.py
+++ b/swh/search/elasticsearch.py
@@ -69,7 +69,7 @@
 
 
 class ElasticSearch:
-    def __init__(self, hosts: List[str], indexes: Dict[str, Dict[str, str]]):
+    def __init__(self, hosts: List[str], indexes: Dict[str, Dict[str, str]] = {}):
         self._backend = Elasticsearch(hosts=hosts)
 
         # Merge current configuration with default values
diff --git a/swh/search/tests/test_server.py b/swh/search/tests/test_server.py
--- a/swh/search/tests/test_server.py
+++ b/swh/search/tests/test_server.py
@@ -18,6 +18,7 @@
 def teardown_function():
     # Ensure there is no configuration loaded from a previous test
     server.api_cfg = None
+    server.search = None
 
 
 def _write_config_file(tmp_path, monkeypatch, content):
@@ -138,11 +139,33 @@
     assert app is app2
 
 
-def test_server_first_call_initialize_elasticsearch(
+def test_server_first_call_initialize_elasticsearch_with_indexes(
     swh_search_config_with_indexes, mocker
 ):
     """Test the initialize method is called during the first and first only
-       request to the server"""
+       request to the server
+        The ElasticSearch object is instantiated only when a request is done
+    """
+    mock = mocker.patch("swh.search.elasticsearch.ElasticSearch.initialize")
+
+    app = make_app_from_configfile()
+    app.config["TESTING"] = True
+    tc = app.test_client()
+
+    tc.get("/")
+    assert mock.call_count == 1
+
+    tc.get("/")
+    assert mock.call_count == 1
+
+
+def test_server_first_call_initialize_elasticsearch_without_indexes(
+    swh_search_config_without_indexes, mocker
+):
+    """Test the initialize method is called during the first and first only
+       request to the server
+       The ElasticSearch object is instantiated only when a request is done
+    """
     mock = mocker.patch("swh.search.elasticsearch.ElasticSearch.initialize")
 
     app = make_app_from_configfile()