diff --git a/python/pyproject.toml b/python/pyproject.toml
index b733b196..f8254042 100644
--- a/python/pyproject.toml
+++ b/python/pyproject.toml
@@ -34,7 +34,7 @@ dependencies = [
 dev = [
   "coverage[toml]>=6.5",
   "pytest>=8.0.2",
-  "syrupy>=4.6.1",
+  "syrupy>=5.0.0",
 ]
 
 # Dependencies for examples.
diff --git a/python/tests/utilities.py b/python/tests/utilities.py
index 174757b2..4e6fc87f 100644
--- a/python/tests/utilities.py
+++ b/python/tests/utilities.py
@@ -12,7 +12,7 @@
 
 class TypeScriptSchemaSnapshotExtension(SingleFileSnapshotExtension):
     _write_mode = WriteMode.TEXT
-    _file_extension = "schema.d.ts"
+    file_extension = "schema.d.ts"
 
     @override
     def serialize(self, data: TypeScriptSchemaConversionResult, *,