diff --git a/addons/project/models/project.py b/addons/project/models/project.py
index edec05a4b62..402a7110038 100644
--- a/addons/project/models/project.py
+++ b/addons/project/models/project.py
@@ -2653,7 +2653,7 @@ class ProjectTags(models.Model):
 
     @api.model
     def _name_search(self, name, domain=None, operator='ilike', limit=None, order=None, name_get_uid=None):
-        if 'project_id' in self.env.context and operator == 'ilike':
+        if self.env.context.get('project_id') and operator == 'ilike':
             # `domain` has the form of the default filter ['!', ['id', 'in', <ids>]]
             # passed to exclude already selected tags -> exclude them in our query too
             excluded_ids = list(domain[1][2]) \
diff --git a/addons/project/tests/test_project_flow.py b/addons/project/tests/test_project_flow.py
index e8b1d171f24..ba00a0b9b41 100644
--- a/addons/project/tests/test_project_flow.py
+++ b/addons/project/tests/test_project_flow.py
@@ -438,3 +438,11 @@ class TestProjectFlow(TestProjectCommon, MailCommon):
 
         self.assertEqual(len(project_A.message_ids), init_nb_log + 2,
             "should have 2 new messages: one for tracking, one for template")
+
+    def test_private_task_search_tag(self):
+        task = self.env['project.task'].create({
+            'name': 'Test Private Task',
+        })
+        # Tag name_search should not raise Error if project_id is False
+        task.tag_ids.with_context(project_id=task.project_id.id).name_search(
+            args=["!", ["id", "in", []]])