diff --git a/gns3server/api/routes/compute/projects.py b/gns3server/api/routes/compute/projects.py
index 2a946c55a..76c88d2f0 100644
--- a/gns3server/api/routes/compute/projects.py
+++ b/gns3server/api/routes/compute/projects.py
@@ -191,8 +191,12 @@ async def create_batch_nios(
         nio_settings = jsonable_encoder(entry.nio, exclude_unset=True)
         # Dynamips.create_nio takes an extra positional `node` argument that
         # the base signature does not include. Detect it via parameter count.
+        # Dynamips.create_nio(self, node, nio_settings) exposes one extra
+        # positional on the bound method compared to the standard signature
+        # (self, nio_settings).  Detect it: standard == 1 bound param,
+        # Dynamips == 2 bound params (node + nio_settings).
         sig = inspect.signature(node.manager.create_nio)
-        if len(sig.parameters) == 3:
+        if len(sig.parameters) >= 2:
             nio = node.manager.create_nio(node, nio_settings)
         else:
             nio = node.manager.create_nio(nio_settings)
diff --git a/tests/api/routes/compute/test_projects.py b/tests/api/routes/compute/test_projects.py
index f491f3c04..b64053d7d 100644
--- a/tests/api/routes/compute/test_projects.py
+++ b/tests/api/routes/compute/test_projects.py
@@ -260,24 +260,25 @@ class TestBatchNIOEdgeCases:
     @pytest.mark.asyncio
     async def test_dynamips_create_nio_passes_node_arg(self):
         """
-        Dynamips.create_nio(self, node, nio_settings) takes an extra 'node'
-        positional; the batch handler detects this via parameter count.
+        Dynamips.create_nio(self, node, nio_settings) exposes 2 bound-method
+        params vs. the standard 1.  The batch handler detects this via the
+        parameter count on the bound method and passes the extra 'node'
+        argument.
         """
         import inspect
 
-        # Dynamips-style 3-param signature (self + node + nio_settings)
-        async def create_nio_with_node(self, node, nio_settings):
-            pass
+        class _FakeDynamips:
+            async def create_nio(self, node, nio_settings):
+                pass
 
-        sig = inspect.signature(create_nio_with_node)
-        assert len(sig.parameters) == 3
+        class _FakeBase:
+            async def create_nio(self, nio_settings):
+                pass
 
-        # Standard base 2-param signature (self + nio_settings)
-        async def create_nio_base(self, nio_settings):
-            pass
-
-        sig2 = inspect.signature(create_nio_base)
-        assert len(sig2.parameters) == 2
+        dyn = _FakeDynamips()
+        base = _FakeBase()
+        assert len(inspect.signature(dyn.create_nio).parameters) == 2   # Dynamips
+        assert len(inspect.signature(base.create_nio).parameters) == 1  # standard
 
     @pytest.mark.asyncio
     async def test_qemu_dispatch_to_adapter_add_nio_binding(self):