diff --git a/tests/test_ywsd_web.py b/tests/test_ywsd_web.py
index 62ba8eb..e16984e 100644
--- a/tests/test_ywsd_web.py
+++ b/tests/test_ywsd_web.py
@@ -33,7 +33,7 @@ def validate_routing_tree(observed, expected):
 
     assert ("fork_ranks" in observed) == ("fork_ranks" in expected)
     if "fork_ranks" in observed:
-        for (observed_rank, expected_rank) in zip(
+        for observed_rank, expected_rank in zip(
             observed["fork_ranks"], expected["fork_ranks"]
         ):
             for key in expected_rank.keys():
@@ -41,7 +41,7 @@ def validate_routing_tree(observed, expected):
                     continue
                 assert observed_rank[key] == expected_rank[key]
         assert len(observed_rank["members"]) == len(expected_rank["members"])
-        for (observed_member, expected_member) in zip(
+        for observed_member, expected_member in zip(
             observed_rank["members"], expected_rank["members"]
         ):
             if "type" in expected_member:
@@ -307,3 +307,34 @@ async def test_webserver_immediate_forward_4748_to_2098(ywsd_engine_web):
             }
             validate_routing_tree(data["routing_tree"], expected_routing_tree)
             assert data["routing_tree"]["forwarding_extension"]["extension"] == "2005"
+
+
+@pytest.mark.asyncio
+@pytest.mark.usefixtures("ywsd_engine_web")
+async def test_webserver_delayed_forward_to_empty_group_4000(ywsd_engine_web):
+    async with aiohttp.ClientSession() as session:
+        async with session.get(
+            "http://localhost:9042/stage1?caller=4748&called=4001"
+        ) as response:
+            data = await response.json()
+            print(repr(data))
+            assert data["routing_status"] == "OK"
+            main_routing_result = data["main_routing_result"]
+            assert main_routing_result["type"] == "Type.FORK"
+            expected_fork_targets = [
+                {
+                    "target": "lateroute/4001",
+                    "parameters": {"eventphone_stage2": "1"},
+                },
+            ]
+            validate_fork_targets(
+                main_routing_result["fork_targets"], expected_fork_targets
+            )
+            expected_routing_tree = {
+                "extension": "4001",
+                "type": "Type.SIMPLE",
+                "forwarding_mode": "ForwardingMode.ENABLED",
+                "forwarding_delay": 10,
+            }
+            validate_routing_tree(data["routing_tree"], expected_routing_tree)
+            assert data["routing_tree"]["forwarding_extension"]["extension"] == "4000"
diff --git a/tests/testdata.py b/tests/testdata.py
index 2c311fa..4d34899 100644
--- a/tests/testdata.py
+++ b/tests/testdata.py
@@ -116,6 +116,26 @@ async def write_testdata(conn):
                     "lang": "de_DE",
                     "ringback": None,
                 },
+                {
+                    "yate_id": None,
+                    "extension": "4000",
+                    "name": "Empty Group",
+                    "type": "GROUP",
+                    "forwarding_mode": "DISABLED",
+                    "forwarding_delay": None,
+                    "lang": "de_DE",
+                    "ringback": None,
+                },
+                {
+                    "yate_id": yates["sip"],
+                    "extension": "4001",
+                    "name": "I Forward to empty group",
+                    "type": "SIMPLE",
+                    "forwarding_mode": "DISABLED",
+                    "forwarding_delay": 10,
+                    "lang": "de_DE",
+                    "ringback": None,
+                },
             ]
         )
     )
@@ -134,6 +154,11 @@ async def write_testdata(conn):
         .where(Extension.table.c.extension == "2098")
         .values({"forwarding_extension_id": exts["2005"], "forwarding_mode": "ENABLED"})
     )
+    await conn.execute(
+        Extension.table.update()
+        .where(Extension.table.c.extension == "4001")
+        .values({"forwarding_extension_id": exts["4000"], "forwarding_mode": "ENABLED"})
+    )
 
     await conn.execute(
         ForkRank.table.insert().values(
diff --git a/tox.ini b/tox.ini
index b2398a1..2725a36 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = py38,py39,py310
+envlist = py38,py39,py310,py311
 skip_missing_interpreters = true
 
 
@@ -11,4 +11,4 @@ deps =
     pytest-black
     pytest-asyncio
     docker
-commands = pytest --black {posargs}
\ No newline at end of file
+commands = pytest --black {posargs}
diff --git a/ywsd/routing_tree.py b/ywsd/routing_tree.py
index dc88152..b7c6088 100644
--- a/ywsd/routing_tree.py
+++ b/ywsd/routing_tree.py
@@ -461,14 +461,17 @@ def _visit_for_route_calculation(
             ):
                 # this is non-immediate forward
                 forwarding_route = self._visit(node.forwarding_extension, local_path)
-                if node.forwarding_mode == Extension.ForwardingMode.ENABLED:
-                    fwd_delay = node.forwarding_delay - accumulated_delay
-                    fork_targets.append(CallTarget("|drop={}".format(fwd_delay)))
-                else:
-                    # Add a default rank, call will progress to next rang when all previous calls failed
-                    fork_targets.append(CallTarget("|"))
-                fork_targets.append(forwarding_route.target)
-                self._cache_intermediate_result(forwarding_route)
+                # if we obtained a valid route, we add this as new fork target here. Otherwise, we keep
+                # the current fork ranks and just move on.
+                if forwarding_route.is_valid:
+                    if node.forwarding_mode == Extension.ForwardingMode.ENABLED:
+                        fwd_delay = node.forwarding_delay - accumulated_delay
+                        fork_targets.append(CallTarget("|drop={}".format(fwd_delay)))
+                    else:
+                        # Add a default rank, call will progress to next rang when all previous calls failed
+                        fork_targets.append(CallTarget("|"))
+                    fork_targets.append(forwarding_route.target)
+                    self._cache_intermediate_result(forwarding_route)
 
             return self._make_intermediate_result(
                 fork_targets=fork_targets,