diff --git a/server/books/blocks.py b/server/books/blocks.py
index a394c383..5343cb7b 100644
--- a/server/books/blocks.py
+++ b/server/books/blocks.py
@@ -28,7 +28,7 @@ class BasicKnowledgeBlock(blocks.StructBlock):
     class Meta:
         icon = 'placeholder'
 
-    description = blocks.RichTextBlock()
+    description = blocks.RichTextBlock(required=False)
     basic_knowledge = blocks.PageChooserBlock(required=True, target_model='basicknowledge.BasicKnowledge')
 
 
diff --git a/server/books/migrations/0011_auto_20190624_1412.py b/server/books/migrations/0011_auto_20190624_1412.py
new file mode 100644
index 00000000..5d644412
--- /dev/null
+++ b/server/books/migrations/0011_auto_20190624_1412.py
@@ -0,0 +1,28 @@
+# Generated by Django 2.0.6 on 2019-06-24 14:12
+
+import assignments.models
+from django.db import migrations, models
+import wagtail.core.blocks
+import wagtail.core.fields
+import wagtail.images.blocks
+import wagtail.snippets.blocks
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('books', '0010_auto_20190312_1306'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='contentblock',
+            name='contents',
+            field=wagtail.core.fields.StreamField([('text_block', wagtail.core.blocks.StructBlock([('text', wagtail.core.blocks.RichTextBlock())])), ('basic_knowledge', wagtail.core.blocks.StructBlock([('description', wagtail.core.blocks.RichTextBlock(required=False)), ('basic_knowledge', wagtail.core.blocks.PageChooserBlock(required=True, target_model=['basicknowledge.BasicKnowledge']))])), ('assignment', wagtail.core.blocks.StructBlock([('assignment_id', wagtail.snippets.blocks.SnippetChooserBlock(assignments.models.Assignment))])), ('image_block', wagtail.images.blocks.ImageChooserBlock()), ('image_url_block', wagtail.core.blocks.StructBlock([('title', wagtail.core.blocks.TextBlock()), ('url', wagtail.core.blocks.URLBlock())])), ('link_block', wagtail.core.blocks.StructBlock([('text', wagtail.core.blocks.TextBlock()), ('url', wagtail.core.blocks.URLBlock())])), ('solution', wagtail.core.blocks.StructBlock([('text', wagtail.core.blocks.RichTextBlock())], icon='tick')), ('video_block', wagtail.core.blocks.StructBlock([('url', wagtail.core.blocks.URLBlock())])), ('document_block', wagtail.core.blocks.StructBlock([('url', wagtail.core.blocks.URLBlock())])), ('infogram_block', wagtail.core.blocks.StructBlock([('id', wagtail.core.blocks.TextBlock()), ('title', wagtail.core.blocks.TextBlock())])), ('genially_block', wagtail.core.blocks.StructBlock([('id', wagtail.core.blocks.TextBlock())]))], blank=True, null=True),
+        ),
+        migrations.AlterField(
+            model_name='contentblock',
+            name='type',
+            field=models.CharField(choices=[('normal', 'Normal'), ('base_communication', 'Instrument Sprache & Kommunikation'), ('task', 'Aufgabe'), ('base_society', 'Instrument Gesellschaft')], default='normal', max_length=100),
+        ),
+    ]