diff --git a/cola/linalg/inv.py b/cola/linalg/inv.py
index 7c6e3591..6e4243d0 100644
--- a/cola/linalg/inv.py
+++ b/cola/linalg/inv.py
@@ -2,8 +2,8 @@
 from plum import dispatch
 from cola.ops import LinearOperator
 from cola.ops import Diagonal, Permutation
-from cola.ops import Identity
-from cola.ops import ScalarMul
+from cola.ops import Identity, Dense
+from cola.ops import ScalarMul, Sum
 from cola.ops import BlockDiag, Triangular
 from cola.ops import Kronecker, Product
 from cola.algorithms.cg import cg
@@ -180,4 +180,4 @@ def inv(A: Sum[Product[Dense,Dense], Diagonal], **kwargs):
 
 @dispatch
 def inv(A: Sum[Diagonal, Product[Dense,Dense]], **kwargs):
-    return inv(Product(*C.Ms[1].Ms) + C.Ms[0])
\ No newline at end of file
+    return inv(Product(*A.Ms[1].Ms) + A.Ms[0])
\ No newline at end of file