From 81559b2c84cc7cc22a071c6f8e4550be6b986207 Mon Sep 17 00:00:00 2001
From: oscarddssmith <oscar.smith@juliacomputing.com>
Date: Tue, 10 Sep 2024 11:27:56 -0400
Subject: [PATCH] fix MatrixOperator mass_matrix

---
 lib/OrdinaryDiffEqDifferentiation/src/derivative_utils.jl | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lib/OrdinaryDiffEqDifferentiation/src/derivative_utils.jl b/lib/OrdinaryDiffEqDifferentiation/src/derivative_utils.jl
index da627a55f8..6c30602ea7 100644
--- a/lib/OrdinaryDiffEqDifferentiation/src/derivative_utils.jl
+++ b/lib/OrdinaryDiffEqDifferentiation/src/derivative_utils.jl
@@ -718,6 +718,9 @@ function calc_W!(W, integrator, nlsolver::Union{Nothing, AbstractNLSolver}, cach
             if W.J isa MatrixOperator
                 J = J.A
             end
+            if mass_matrix isa MatrixOperator
+                mass_matrix = mass_matrix.A
+            end
             if new_W && !isdae
                 jacobian2W!(W._concrete_form, mass_matrix, dtgamma, J, W_transform)
             end