diff --git a/.htaccess b/.htaccess
index 01c63af..692ae8c 100644
--- a/.htaccess
+++ b/.htaccess
@@ -120,7 +120,7 @@ AddEncoding gzip svgz
   #
   # If your site is running in a VirtualDocumentRoot at http://example.com/,
   # uncomment the following line:
-  # RewriteBase /
+  RewriteBase /
 
   # Redirect common PHP files to their new locations.
   RewriteCond %{REQUEST_URI} ^(.*)?/(install.php) [OR]
diff --git a/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php b/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php
index 1e47d1a..7f97464 100644
--- a/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php
+++ b/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php
@@ -287,6 +287,7 @@ protected function ensureTables() {
       foreach ($this->migration->getSourcePlugin()->getIds() as $id_definition) {
         $mapkey = 'sourceid' . $count++;
         $source_id_schema[$mapkey] = $this->getFieldSchema($id_definition);
+        $source_id_schema[$mapkey]['not null'] = TRUE;
 
         // With InnoDB, utf8mb4-based primary keys can't be over 191 characters.
         // Use ASCII-based primary keys instead.