diff --git a/Lib/inspect.py b/Lib/inspect.py
index 0273ffa..750fd45 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -2471,15 +2471,23 @@ def _signature_from_callable(obj, *,
         if call is not None:
             sig = _get_signature_of(call)
         else:
-            # Now we check if the 'obj' class has a '__new__' method
+            factory_method = None
             new = _signature_get_user_defined_method(obj, '__new__')
-            if new is not None:
-                sig = _get_signature_of(new)
-            else:
-                # Finally, we should have at least __init__ implemented
-                init = _signature_get_user_defined_method(obj, '__init__')
-                if init is not None:
-                    sig = _get_signature_of(init)
+            init = _signature_get_user_defined_method(obj, '__init__')
+            # Now we check if the 'obj' class has an own '__new__' method
+            if '__new__' in obj.__dict__:
+                factory_method = new
+            # or an own '__init__' method
+            elif '__init__' in obj.__dict__:
+                factory_method = init
+            # If not, we take inherited '__new__' or '__init__', if present
+            elif new is not None:
+                factory_method = new
+            elif init is not None:
+                factory_method = init
+
+            if factory_method is not None:
+                sig = _get_signature_of(factory_method)
 
         if sig is None:
             # At this point we know, that `obj` is a class, with no user-