diff --git a/test/test_store.py b/test/test_store.py
index 58ea2c5..ccce7b2 100644
--- a/test/test_store.py
+++ b/test/test_store.py
@@ -190,7 +190,7 @@ def test_get_open_data_params_schema(self):
             self.assertEqual(1, len(w))
             warn_msg = (
                 f"The data ID '{self.data_id_netcdf}' contains the formats "
-                "['geotiff', 'netcdf']. Please, do not specify 'opener_id' as "
+                "['geotiff' 'netcdf']. Please, do not specify 'opener_id' as "
                 "multiple openers will be used."
             )
             self.assertEqual(warn_msg, str(w[-1].message))
diff --git a/xcube_stac/store.py b/xcube_stac/store.py
index aeca5e2..6615b20 100644
--- a/xcube_stac/store.py
+++ b/xcube_stac/store.py
@@ -156,7 +156,7 @@ def get_open_data_params_schema(
             formats = _get_formats_from_item(item)
             if len(formats) != 1:
                 warnings.warn(
-                    f"The data ID '{data_id}' contains the formats {list(formats)}. "
+                    f"The data ID '{data_id}' contains the formats {formats}. "
                     "Please, do not specify 'opener_id' as multiple openers "
                     "will be used."
                 )