diff --git a/psydac/linalg/basic.py b/psydac/linalg/basic.py
index 07ff42670..81079a5c7 100644
--- a/psydac/linalg/basic.py
+++ b/psydac/linalg/basic.py
@@ -279,7 +279,7 @@ def __neg__(self):
         a new object of the class ScaledLinearOperator.
         
         """
-        return ScaledLinearOperator(self._domain, self._codomain, -1.0, self)
+        return ScaledLinearOperator(self.domain, self.codomain, -1.0, self)
 
     def __mul__(self, c):
         """