diff --git a/ptulsconv/docparser/pt_doc_parser.py b/ptulsconv/docparser/pt_doc_parser.py
index b9553df..4cc616d 100644
--- a/ptulsconv/docparser/pt_doc_parser.py
+++ b/ptulsconv/docparser/pt_doc_parser.py
@@ -108,8 +108,12 @@ def parse_document(session_text: str) -> SessionDescriptor:
 
 class DocParserVisitor(NodeVisitor):
 
-    @staticmethod
-    def visit_document(_, visited_children) -> SessionDescriptor:
+    def __init__(self):
+        self.track_index = 0
+
+    # @staticmethod
+    def visit_document(self, _, visited_children) -> SessionDescriptor:
+        self.track_index = 0
         files = next(iter(visited_children[1]), None)
         clips = next(iter(visited_children[2]), None)
         plugins = next(iter(visited_children[3]), None)
@@ -196,8 +200,8 @@ class DocParserVisitor(NodeVisitor):
     def visit_frame_rate(node, _):
         return node.text
 
-    def visit_track_listing(self, _, visited_children):
-        self.track_index = 0
+    @staticmethod
+    def visit_track_listing(_, visited_children):
         return visited_children[1]
 
     @staticmethod
diff --git a/tests/unittests/test_tag_compiler.py b/tests/unittests/test_tag_compiler.py
index db4e4fb..d24e9b8 100644
--- a/tests/unittests/test_tag_compiler.py
+++ b/tests/unittests/test_tag_compiler.py
@@ -88,7 +88,9 @@ class TestTagCompiler(unittest.TestCase):
                                            state='Unmuted',
                                            timestamp=None),
         ]
-        test_track = doc_entity.TrackDescriptor(name="Track 1 [A] {Color=Red} $Mode=1",
+        test_track = doc_entity.TrackDescriptor(
+            index=0,
+            name="Track 1 [A] {Color=Red} $Mode=1",
                                                 comments="{Comment=This is some text in the comments}",
                                                 user_delay_samples=0,
                                                 plugins=[],