diff --git a/lang/src/main/antlr4/edu/kit/iti/formal/psdbg/parser/ScriptLanguage.g4 b/lang/src/main/antlr4/edu/kit/iti/formal/psdbg/parser/ScriptLanguage.g4
index 6545e2f7973f306d5c0d9221bab8658c935a829e..b015955e5528ff78f1032e7d220f64cc7d3e1ef8 100644
--- a/lang/src/main/antlr4/edu/kit/iti/formal/psdbg/parser/ScriptLanguage.g4
+++ b/lang/src/main/antlr4/edu/kit/iti/formal/psdbg/parser/ScriptLanguage.g4
@@ -212,4 +212,4 @@ QUESTION_MARK: '?';
 
 DIGITS : DIGIT+ ;
 fragment DIGIT : [0-9] ;
-ID : ([a-zA-Z]|'#') ([_a-zA-Z0-9] | '.' | '\\'| '#')*;
\ No newline at end of file
+ID : ([a-zA-Z]|'#'|'_') ([_a-zA-Z0-9] | '.' | '\\'| '#')*;
\ No newline at end of file
diff --git a/rt/src/main/java/edu/kit/iti/formal/psdbg/interpreter/assignhook/DefaultAssignmentHook.java b/rt/src/main/java/edu/kit/iti/formal/psdbg/interpreter/assignhook/DefaultAssignmentHook.java
index 816405d9cae717931e1ddcdb116819bac1c095e2..61e98013114620f038794900a3d8c17e5fb16b2d 100644
--- a/rt/src/main/java/edu/kit/iti/formal/psdbg/interpreter/assignhook/DefaultAssignmentHook.java
+++ b/rt/src/main/java/edu/kit/iti/formal/psdbg/interpreter/assignhook/DefaultAssignmentHook.java
@@ -39,7 +39,8 @@ public abstract class DefaultAssignmentHook<T> implements VariableAssignmentHook
             Variable<T, S> variable = (Variable<T, S>) variables.get(variableName);
             return variable.setter.apply(data, value);
         }
-        return true;
+        //@AW: TODO was true: Why?
+        return false;
     }