diff --git a/key.util/src/main/java/org/key_project/util/bean/Bean.java b/key.util/src/main/java/org/key_project/util/bean/Bean.java
index 04c5899a2ca..9eae6c0cb14 100644
--- a/key.util/src/main/java/org/key_project/util/bean/Bean.java
+++ b/key.util/src/main/java/org/key_project/util/bean/Bean.java
@@ -6,6 +6,9 @@
 
 import org.key_project.util.java.ArrayUtil;
 
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
 /**
  * Implements the basic methods that a Java bean should have and is the default implementation of
  * {@link IBean}.
@@ -13,11 +16,12 @@
  * @author Martin Hentschel
  * @see IBean
  */
-@SuppressWarnings("nullness")
+@NullMarked
 public class Bean implements IBean {
     /**
      * The used {@link PropertyChangeSupport}.
      */
+    @SuppressWarnings("nullness") // TODO Check with Werner Dietl why this is so.
     private final PropertyChangeSupport pcs = new PropertyChangeSupport(this);
 
     /**
@@ -127,8 +131,8 @@ protected void fireIndexedPropertyChange(String propertyName, int index, int old
      * @param oldValue The old value.
      * @param newValue The new value.
      */
-    protected void fireIndexedPropertyChange(String propertyName, int index, Object oldValue,
-            Object newValue) {
+    protected void fireIndexedPropertyChange(String propertyName, int index,
+            @Nullable Object oldValue, @Nullable Object newValue) {
         pcs.fireIndexedPropertyChange(propertyName, index, oldValue, newValue);
     }
 
diff --git a/key.util/src/main/java/org/key_project/util/bean/IBean.java b/key.util/src/main/java/org/key_project/util/bean/IBean.java
index 1706fcd6b16..ff71eb17169 100644
--- a/key.util/src/main/java/org/key_project/util/bean/IBean.java
+++ b/key.util/src/main/java/org/key_project/util/bean/IBean.java
@@ -2,6 +2,8 @@
 
 import java.beans.PropertyChangeListener;
 
+import org.jspecify.annotations.NullMarked;
+
 /**
  * <p>
  * Defines the methods that a Java bean must have.
@@ -13,6 +15,7 @@
  * @author Martin Hentschel
  * @see Bean
  */
+@NullMarked
 public interface IBean {
     /**
      * Adds the given listener.
diff --git a/key.util/src/main/java/org/key_project/util/java/ArrayUtil.java b/key.util/src/main/java/org/key_project/util/java/ArrayUtil.java
index 2ce18fcbbd2..5c5d780b656 100644
--- a/key.util/src/main/java/org/key_project/util/java/ArrayUtil.java
+++ b/key.util/src/main/java/org/key_project/util/java/ArrayUtil.java
@@ -1,13 +1,13 @@
 package org.key_project.util.java;
 
-import org.jspecify.annotations.NullMarked;
-import org.jspecify.annotations.Nullable;
-
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Objects;
 import java.util.function.Predicate;
 
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
 /**
  * Provides static methods to work with arrays.
  *
@@ -60,25 +60,26 @@ private ArrayUtil() {
      * @throws IllegalArgumentException Both parameters are {@code null}.
      */
     @SuppressWarnings("unchecked")
-    public static <T extends @Nullable Object> T [] addAll(T @Nullable [] array, T @Nullable [] toAdd) {
+    public static <T extends @Nullable Object> T[] addAll(T @Nullable [] array,
+            T @Nullable [] toAdd) {
         if (array != null) {
             if (toAdd != null) {
                 T[] result =
-                    (T[]) java.lang.reflect.Array.newInstance(array.getClass().getComponentType(),
+                    (T[]) java.lang.reflect.Array.newInstance(getComponentType(array),
                         array.length + toAdd.length);
                 System.arraycopy(array, 0, result, 0, array.length);
                 System.arraycopy(toAdd, 0, result, array.length, toAdd.length);
                 return result;
             } else {
                 T[] result = (T[]) java.lang.reflect.Array
-                        .newInstance(array.getClass().getComponentType(), array.length);
+                        .newInstance(getComponentType(array), array.length);
                 System.arraycopy(array, 0, result, 0, array.length);
                 return result;
             }
         } else {
             if (toAdd != null) {
                 T[] result = (T[]) java.lang.reflect.Array
-                        .newInstance(toAdd.getClass().getComponentType(), toAdd.length);
+                        .newInstance(getComponentType(toAdd), toAdd.length);
                 System.arraycopy(toAdd, 0, result, 0, toAdd.length);
                 return result;
             } else {
@@ -88,6 +89,12 @@ private ArrayUtil() {
         }
     }
 
+    private static <T extends @Nullable Object> Class<? extends T> getComponentType(T[] array) {
+        Class<? extends Object[]> arrayClass = array.getClass();
+        assert arrayClass.isArray() : "@AssumeAssertion(nullness): This is always the case";
+        return (Class<? extends T>) arrayClass.getComponentType();
+    }
+
     /**
      * <p>
      * Adds the given elements to the existing array. The result is a new array that contains the
@@ -105,7 +112,8 @@ private ArrayUtil() {
      * @throws IllegalArgumentException Both parameters are {@code null}.
      */
     @SuppressWarnings("unchecked")
-    public static <T extends @Nullable Object> T[] addAll(T @Nullable [] array, T @Nullable [] toAdd, Class<?> newArrayType) {
+    public static <T extends @Nullable Object> T[] addAll(T @Nullable [] array,
+            T @Nullable [] toAdd, Class<?> newArrayType) {
         if (array != null) {
             if (toAdd != null) {
                 T[] result = (T[]) java.lang.reflect.Array.newInstance(newArrayType,
@@ -145,10 +153,12 @@ private ArrayUtil() {
      * @throws IllegalArgumentException Both parameters are {@code null}.
      */
     @SuppressWarnings("unchecked")
-    public static <T extends @Nullable Object> T[] add(T @Nullable [] array, @Nullable T toAdd) {
+    public static <T extends @Nullable Object> @Nullable T[] add(T @Nullable [] array,
+            @Nullable T toAdd) {
         if (array != null) {
-            T[] result = (T[]) java.lang.reflect.Array
-                    .newInstance(array.getClass().getComponentType(), array.length + 1);
+            @Nullable
+            T[] result = (@Nullable T[]) java.lang.reflect.Array
+                    .newInstance(getComponentType(array), array.length + 1);
             System.arraycopy(array, 0, result, 0, array.length);
             result[array.length] = toAdd;
             return result;
@@ -200,7 +210,7 @@ public static int[] add(int[] array, int toAdd) {
     public static <T> T[] insert(T[] array, T toInsert, int index) {
         if (array != null) {
             T[] result = (T[]) java.lang.reflect.Array
-                    .newInstance(array.getClass().getComponentType(), array.length + 1);
+                    .newInstance(getComponentType(array), array.length + 1);
             if (index >= 1) {
                 System.arraycopy(array, 0, result, 0, index);
             }
@@ -263,7 +273,8 @@ public static <T> int indexOf(T[] array, T toSearch) {
      *         was {@code null}.
      */
     @SuppressWarnings("unchecked")
-    public static <T> T[] remove(T[] array, T toRemove) {
+    public static <T extends @Nullable Object> T @Nullable [] remove(T @Nullable [] array,
+            @Nullable T toRemove) {
         if (array != null) {
             List<T> result = new LinkedList<>();
             for (T element : array) {
@@ -271,8 +282,8 @@ public static <T> T[] remove(T[] array, T toRemove) {
                     result.add(element);
                 }
             }
-            return result.toArray((T[]) java.lang.reflect.Array
-                    .newInstance(array.getClass().getComponentType(), result.size()));
+            return (T[]) result.toArray((T[]) java.lang.reflect.Array
+                    .newInstance(getComponentType(array), result.size()));
         } else {
             return null;
         }