diff --git a/code/aussagenlogik/schema.py b/code/aussagenlogik/schema.py
index 0e73aa0..59d25ac 100644
--- a/code/aussagenlogik/schema.py
+++ b/code/aussagenlogik/schema.py
@@ -9,9 +9,6 @@ from __future__ import annotations;
 # install: lark; lark-parser; lark-parser[regex].
 # https://lark-parser.readthedocs.io/en/latest/grammar.html
 from lark import Lark;
-from lark import Tree;
-from typing import List;
-from typing import Union;
 
 from aussagenlogik.syntaxbaum import SyntaxBaum;
 
@@ -66,7 +63,7 @@ def isDisjunction(fml: SyntaxBaum) -> bool:
     return fml.kind == 'disj';
 
 def isLongDisjunction(fml: SyntaxBaum) -> bool:
-    return fml.kind == ['disj', 'disj_lang'];
+    return fml.kind in ['disj', 'disj_lang'];
 
 def isImplication(fml: SyntaxBaum) -> bool:
     return fml.kind == 'impl';