diff --git a/lib/Migration/Version000013Date20190723185417.php b/lib/Migration/Version000013Date20190723185417.php
index db089278c..95f1e2b46 100644
--- a/lib/Migration/Version000013Date20190723185417.php
+++ b/lib/Migration/Version000013Date20190723185417.php
@@ -44,7 +44,7 @@ public function changeSchema(IOutput $output, Closure $schemaClosure, array $opt
 			$table->dropColumn('contact_uid');
 			$table->addColumn('object_uri', 'string', [
 				'notnull' => true,
-				'default' => '',
+				'default' => '--',
 				'length' => 64,
 			]);
 			$table->addIndex(['object_uri'], 'maps_object_uri');
diff --git a/lib/Migration/Version000102Date20190901152326.php b/lib/Migration/Version000102Date20190901152326.php
index 29f1f38d0..cf75ac9b1 100644
--- a/lib/Migration/Version000102Date20190901152326.php
+++ b/lib/Migration/Version000102Date20190901152326.php
@@ -43,7 +43,7 @@ public function changeSchema(IOutput $output, Closure $schemaClosure, array $opt
 			$table = $schema->getTable('maps_address_geo');
 			$table->changeColumn('object_uri', [
 				'notnull' => true,
-				'default' => '',
+				'default' => '--',
 				'length' => 255,
 			]);
 		}