diff --git a/src/lib/Form/Type/FieldType/ImageAssetFieldType.php b/src/lib/Form/Type/FieldType/ImageAssetFieldType.php
index ce72fa1e..6ddf466b 100644
--- a/src/lib/Form/Type/FieldType/ImageAssetFieldType.php
+++ b/src/lib/Form/Type/FieldType/ImageAssetFieldType.php
@@ -86,6 +86,7 @@ public function buildForm(FormBuilderInterface $builder, array $options)
                 TextType::class,
                 [
                     'label' => /** @Desc("Alternative text") */ 'content.field_type.ezimageasset.alternative_text',
+                    'block_prefix' => 'ibexa_fieldtype_ezimage_alternative_text',
                 ]
             );
     }
diff --git a/src/lib/Form/Type/FieldType/ImageFieldType.php b/src/lib/Form/Type/FieldType/ImageFieldType.php
index 9f0c25ab..240e81ae 100644
--- a/src/lib/Form/Type/FieldType/ImageFieldType.php
+++ b/src/lib/Form/Type/FieldType/ImageFieldType.php
@@ -54,6 +54,7 @@ public function buildForm(FormBuilderInterface $builder, array $options)
                 [
                     'label' => /** @Desc("Alternative text") */ 'content.field_type.ezimage.alternative_text',
                     'required' => $options['is_alternative_text_required'],
+                    'block_prefix' => 'ibexa_fieldtype_ezimage_alternative_text',
                 ]
             )
             ->add(