diff --git a/sphinx/domains/python.py b/sphinx/domains/python.py
index cf13479d1f4..e31a7c26a63 100644
--- a/sphinx/domains/python.py
+++ b/sphinx/domains/python.py
@@ -305,7 +305,7 @@ def parse(self) -> None:
                         tokens = self.fetch_type_param_spec()
                         tp_ann = self._build_identifier(tokens)
 
-                    if current == [token.OP, '=']:
+                    if self.current and self.current == [token.OP, '=']:
                         tokens = self.fetch_type_param_spec()
                         tp_default = self._build_identifier(tokens)