diff --git a/tableauserverclient/models/workbook_item.py b/tableauserverclient/models/workbook_item.py
index 949970ced..583d2883c 100644
--- a/tableauserverclient/models/workbook_item.py
+++ b/tableauserverclient/models/workbook_item.py
@@ -124,7 +124,6 @@ def project_id(self) -> Optional[str]:
         return self._project_id
 
     @project_id.setter
-    @property_not_nullable
     def project_id(self, value: str):
         self._project_id = value
 
diff --git a/test/test_workbook_model.py b/test/test_workbook_model.py
index d45899e2d..fc6423564 100644
--- a/test/test_workbook_model.py
+++ b/test/test_workbook_model.py
@@ -4,12 +4,6 @@
 
 
 class WorkbookModelTests(unittest.TestCase):
-    def test_invalid_project_id(self):
-        self.assertRaises(ValueError, TSC.WorkbookItem, None)
-        workbook = TSC.WorkbookItem("10")
-        with self.assertRaises(ValueError):
-            workbook.project_id = None
-
     def test_invalid_show_tabs(self):
         workbook = TSC.WorkbookItem("10")
         with self.assertRaises(ValueError):