diff --git a/src/main/angular/src/app/api/tools/Numbers/Numbers.ts b/src/main/angular/src/app/api/tools/Numbers/Numbers.ts
index 6b16336..5fa9f89 100644
--- a/src/main/angular/src/app/api/tools/Numbers/Numbers.ts
+++ b/src/main/angular/src/app/api/tools/Numbers/Numbers.ts
@@ -1,5 +1,5 @@
 import {Group} from "../../group/Group";
-import {validateDate, validateNumber, validateString} from "../../common/validators";
+import {validateDate, validateNumberOrNull, validateString} from "../../common/validators";
 
 export class Numbers {
 
@@ -7,7 +7,7 @@ export class Numbers {
     readonly uuid: string,
     readonly group: Group,
     readonly date: Date,
-    readonly number: number,
+    readonly number: number | null,
   ) {
     // -
   }
@@ -17,7 +17,7 @@ export class Numbers {
       validateString(json['uuid']),
       Group.fromJson(json['group']),
       validateDate(json['date']),
-      validateNumber(json['number']),
+      validateNumberOrNull(json['number']),
     );
   }
 
diff --git a/src/main/angular/src/app/pages/group/group/group.component.html b/src/main/angular/src/app/pages/group/group/group.component.html
index bacbae2..37d7d9c 100644
--- a/src/main/angular/src/app/pages/group/group/group.component.html
+++ b/src/main/angular/src/app/pages/group/group/group.component.html
@@ -59,7 +59,7 @@
             <table>
               <tr class="number" *ngFor="let numbers of numbersList.content">
                 <td>{{ numbers.date | relative:now }}</td>
-                <td>{{ numbers.number }}</td>
+                <td>{{ numbers.number || '-' }}</td>
               </tr>
             </table>
           </div>
diff --git a/src/main/angular/src/app/pages/tools/numbers/numbers.component.html b/src/main/angular/src/app/pages/tools/numbers/numbers.component.html
index 190fb1e..504ed6d 100644
--- a/src/main/angular/src/app/pages/tools/numbers/numbers.component.html
+++ b/src/main/angular/src/app/pages/tools/numbers/numbers.component.html
@@ -14,7 +14,7 @@
   </div>
 
   <div class="huge">
-    {{ numbers.number }}
+    {{ numbers.number || '-' }}
   </div>
 
 </div>
diff --git a/src/main/java/de/ph87/tools/tools/numbers/Numbers.java b/src/main/java/de/ph87/tools/tools/numbers/Numbers.java
index 96af1e6..db57446 100644
--- a/src/main/java/de/ph87/tools/tools/numbers/Numbers.java
+++ b/src/main/java/de/ph87/tools/tools/numbers/Numbers.java
@@ -5,6 +5,7 @@ import de.ph87.tools.tools.numbers.uuid.NumbersAbstract;
 import de.ph87.tools.tools.numbers.uuid.NumbersUuid;
 import de.ph87.tools.user.User;
 import de.ph87.tools.user.reference.UserReference;
+import jakarta.annotation.Nullable;
 import jakarta.persistence.*;
 import lombok.*;
 
@@ -53,14 +54,15 @@ public class Numbers extends NumbersAbstract {
     this.users = users;
   }
 
-  public int getNumberForUser(@NonNull final User user) {
+  @Nullable
+  public Integer getNumberForUser(@NonNull final User user) {
     for (int userReferenceIndex = 0; userReferenceIndex < users.size(); userReferenceIndex++) {
       final UserReference userReference = users.get(userReferenceIndex);
       if (userReference.getUser() != null && userReference.getUser().equals(user)) {
         return userReferenceIndex + 1;
       }
     }
-    throw new RuntimeException();
+    return null;
   }
 
   public boolean containsUser(@NonNull final User user) {
diff --git a/src/main/java/de/ph87/tools/tools/numbers/NumbersDto.java b/src/main/java/de/ph87/tools/tools/numbers/NumbersDto.java
index 5dcd20d..495d762 100644
--- a/src/main/java/de/ph87/tools/tools/numbers/NumbersDto.java
+++ b/src/main/java/de/ph87/tools/tools/numbers/NumbersDto.java
@@ -5,6 +5,7 @@ import de.ph87.tools.common.uuid.UuidSerializer;
 import de.ph87.tools.group.GroupDto;
 import de.ph87.tools.tools.numbers.uuid.NumbersAbstract;
 import de.ph87.tools.tools.numbers.uuid.NumbersUuid;
+import jakarta.annotation.Nullable;
 import lombok.Getter;
 import lombok.NonNull;
 import lombok.ToString;
@@ -25,9 +26,10 @@ public class NumbersDto extends NumbersAbstract {
   @NonNull
   private final ZonedDateTime date;
 
-  private final int number;
+  @Nullable
+  private final Integer number;
 
-  public NumbersDto(@NonNull final Numbers numbers, @NonNull final GroupDto group, final int number) {
+  public NumbersDto(@NonNull final Numbers numbers, @NonNull final GroupDto group, @Nullable final Integer number) {
     this.uuid = numbers.getUuid();
     this.date = numbers.getDate();
     this.group = group;
diff --git a/src/main/java/de/ph87/tools/tools/numbers/NumbersService.java b/src/main/java/de/ph87/tools/tools/numbers/NumbersService.java
index 17197cf..abd5d11 100644
--- a/src/main/java/de/ph87/tools/tools/numbers/NumbersService.java
+++ b/src/main/java/de/ph87/tools/tools/numbers/NumbersService.java
@@ -71,7 +71,7 @@ public class NumbersService {
   @NonNull
   public NumbersDto toDto(@NonNull final Numbers numbers, @NonNull final User user) {
     final GroupDto group = groupService.toDto(numbers.getGroup());
-    final int number = numbers.getNumberForUser(user);
+    final Integer number = numbers.getNumberForUser(user);
     return new NumbersDto(numbers, group, number);
   }