diff --git a/pytest_textual_snapshot.py b/pytest_textual_snapshot.py
index 44c5fd4..902a002 100644
--- a/pytest_textual_snapshot.py
+++ b/pytest_textual_snapshot.py
@@ -31,12 +31,12 @@ if TYPE_CHECKING:
 
 
 class SVGImageExtension(SingleFileSnapshotExtension):
-    _file_extension = "svg"
+    file_extension = "svg"
     _write_mode = WriteMode.TEXT
 
-    def _read_snapshot_data_from_location(self, *args, **kwargs) -> Optional["SerializableData"]:
+    def read_snapshot_data_from_location(self, *args, **kwargs) -> Optional["SerializableData"]:
         """Normalize SVG data right after they are loaded from persistent storage."""
-        data = super()._read_snapshot_data_from_location(*args, **kwargs)
+        data = super().read_snapshot_data_from_location(*args, **kwargs)
         if data is not None:
             data = normalize_svg(data)
         return data
@@ -305,6 +305,8 @@ def retrieve_svg_diffs(
     pass_count = 0
 
     n = 0
+    if not Path(tempdir.name).exists():
+        return diffs, pass_count
     for data_path in Path(tempdir.name).iterdir():
         (
             passed,