diff --git a/src/Entity/ProjectSystem/Project.php b/src/Entity/ProjectSystem/Project.php
index f51d34b5..2dbd9196 100644
--- a/src/Entity/ProjectSystem/Project.php
+++ b/src/Entity/ProjectSystem/Project.php
@@ -31,6 +31,7 @@ use Doctrine\Common\Collections\Collection;
 use Doctrine\ORM\Mapping as ORM;
 use InvalidArgumentException;
 use Symfony\Component\Validator\Constraints as Assert;
+use Symfony\Component\Validator\Context\ExecutionContextInterface;
 
 /**
  * Class AttachmentType.
@@ -280,6 +281,34 @@ class Project extends AbstractStructuralDBElement
         }
     }
 
+    /**
+     * @Assert\Callback
+     */
+    public function validate(ExecutionContextInterface $context, $payload)
+    {
+        //If this project has subprojects, and these have builds part, they must be included in the BOM
+        foreach ($this->getChildren() as $child) {
+            /** @var $child Project */
+            if ($child->getBuildPart() === null) {
+                continue;
+            }
+            //We have to search all bom entries for the build part
+            $found = false;
+            foreach ($this->getBomEntries() as $bom_entry) {
+                if ($bom_entry->getPart() === $child->getBuildPart()) {
+                    $found = true;
+                    break;
+                }
+            }
 
-
+            //When the build part is not found, we have to add an error
+            if (!$found) {
+                $context->buildViolation('project.bom_has_to_include_all_subelement_parts')
+                    ->atPath('bom_entries')
+                    ->setParameter('%project_name%', $child->getName())
+                    ->setParameter('%part_name%', $child->getBuildPart()->getName())
+                    ->addViolation();
+            }
+        }
+    }
 }
diff --git a/templates/AdminPages/DeviceAdmin.html.twig b/templates/AdminPages/DeviceAdmin.html.twig
index 17502956..f21c685a 100644
--- a/templates/AdminPages/DeviceAdmin.html.twig
+++ b/templates/AdminPages/DeviceAdmin.html.twig
@@ -41,6 +41,7 @@
 {% block additional_panes %}
     <div class="tab-pane" id="bom">
         {% form_theme form.bom_entries with ['Form/collection_types_layout.html.twig'] %}
+        {{ form_errors(form.bom_entries) }}
         {{ form_widget(form.bom_entries) }}
     </div>
 {% endblock %}
\ No newline at end of file
diff --git a/translations/validators.en.xlf b/translations/validators.en.xlf
index f7425fde..a1983bb2 100644
--- a/translations/validators.en.xlf
+++ b/translations/validators.en.xlf
@@ -269,5 +269,11 @@
         <target>You can not add a project's own builds part to the BOM.</target>
       </segment>
     </unit>
+    <unit id="2x2XDI_" name="project.bom_has_to_include_all_subelement_parts">
+      <segment>
+        <source>project.bom_has_to_include_all_subelement_parts</source>
+        <target>The project BOM has to include all subprojects builds parts. Part %part_name% of project %project_name% missing!</target>
+      </segment>
+    </unit>
   </file>
 </xliff>