diff --git a/test/webapi/viewer/test_routes.py b/test/webapi/viewer/test_routes.py
index e48cf9e44..0763c2e90 100644
--- a/test/webapi/viewer/test_routes.py
+++ b/test/webapi/viewer/test_routes.py
@@ -33,12 +33,12 @@ class ViewerStateRoutesNoConfigTest(RoutesTestCase):
 
     def test_get(self):
         response = self.fetch("/viewer/state")
-        self.assertEqual(504, response.status)
+        self.assertEqual(501, response.status)
         self.assertEqual("Persistence not supported", response.reason)
 
     def test_put(self):
         response = self.fetch("/viewer/state", method="PUT", body={"state": 123})
-        self.assertEqual(504, response.status)
+        self.assertEqual(501, response.status)
         self.assertEqual("Persistence not supported", response.reason)
 
 
diff --git a/xcube/webapi/viewer/routes.py b/xcube/webapi/viewer/routes.py
index f9cd733fd..c159ddcef 100644
--- a/xcube/webapi/viewer/routes.py
+++ b/xcube/webapi/viewer/routes.py
@@ -124,7 +124,8 @@ class ViewerStateHandler(ApiHandler[ViewerContext]):
     )
     def get(self):
         if self.ctx.persistence is None:
-            self.response.set_status(504, "Persistence not supported")
+            # 501: Not Implemented
+            self.response.set_status(501, "Persistence not supported")
             return
         key = self.request.get_query_arg("key", type=str, default="")
         if key:
@@ -144,7 +145,8 @@ def get(self):
     )
     def put(self):
         if self.ctx.persistence is None:
-            self.response.set_status(504, "Persistence not supported")
+            # 501: Not Implemented
+            self.response.set_status(501, "Persistence not supported")
             return
         state = self.request.body
         key = self.new_key()