diff --git a/setup.py b/setup.py
index da14759ca..cd6d1f180 100644
--- a/setup.py
+++ b/setup.py
@@ -93,6 +93,8 @@ def _get_class_info_from_source(source: str) -> Tuple[str, Optional[str]]:
     base = class_def.bases[0]
     if isinstance(base, ast.Name):
         parent_class = base.id
+    elif isinstance(base, ast.Subscript):
+        parent_class = base.value.id
     else:
         # NOTE: SSZ definition derives from earlier phase...
         # e.g. `phase0.SignedBeaconBlock`
@@ -216,10 +218,19 @@ def get_spec(file_name: Path, preset: Dict[str, str], config: Dict[str, str], pr
                 class_name, parent_class = _get_class_info_from_source(source)
                 # check consistency with spec
                 assert class_name == current_name
+                ignore_type = False
                 if parent_class:
-                    assert parent_class == "Container"
+                    if parent_class == "Container":
+                        pass
+                    elif parent_class == "Vector":
+                        ignore_type = True  # Avoid Mypy error: Invalid base class "Vector"
+                    else:
+                        raise Exception("unrecognized parent class: " + source)
                 # NOTE: trim whitespace from spec
-                ssz_objects[current_name] = "\n".join(line.rstrip() for line in source.splitlines())
+                lines = [line.rstrip() for line in source.splitlines()]
+                if ignore_type:
+                    lines[0] += "  # type: ignore"
+                ssz_objects[current_name] = "\n".join(lines)
             else:
                 raise Exception("unrecognized python code element: " + source)
         elif isinstance(child, Table):