diff --git a/.github/workflows/run-tests.yml b/.github/workflows/run-tests.yml
index e573a9c..69c756c 100644
--- a/.github/workflows/run-tests.yml
+++ b/.github/workflows/run-tests.yml
@@ -2,9 +2,9 @@ name: run-tests
 
 on:
   push:
-    branches: [master]
+    branches: [main]
   pull_request:
-    branches: [master]
+    branches: [main]
 
 jobs:
   test:
diff --git a/config/tenantable.php b/config/tenantable.php
index 02b1bf7..813e0b9 100644
--- a/config/tenantable.php
+++ b/config/tenantable.php
@@ -8,6 +8,13 @@
 
     'related_tenant_column' => env('TENANTABLE_RELATED_TENANT_COLUMN', 'tenant_id'),
 
+    /**
+     * Allow the `tenant_id` to be null.
+     *
+     * If the entry does have null tenant_id, it will be considered as a global entry.
+     */
+    'allow_nullable_tenant' => env('ALLOW_NULLABLE_TENANT', true),
+
     /**
      * The base model for tenant.
      */
diff --git a/src/Models/TenantScope.php b/src/Models/TenantScope.php
index ba5451b..47eec83 100644
--- a/src/Models/TenantScope.php
+++ b/src/Models/TenantScope.php
@@ -10,7 +10,17 @@ class TenantScope implements Scope
 {
     public function apply(Builder $builder, Model $model)
     {
-        $builder->where($model->qualifyColumn(config('tenantable.related_tenant_column')), tenant()->key());
+        $column = $model->qualifyColumn(config('tenantable.related_tenant_column'));
+        $tenantKey = tenant()->key();
+
+        if (config('tenantable.allow_nullable_tenant')) {
+            $builder->where(function (Builder $query) use ($column, $tenantKey) {
+                $query->whereNull($column)
+                    ->orWhere($column, $tenantKey);
+            });
+        } else {
+            $builder->where($column, $tenantKey);
+        }
     }
 
     public function extend(Builder $builder)