diff --git a/dedalus/core/solvers.py b/dedalus/core/solvers.py
index b333b794..84666b3e 100644
--- a/dedalus/core/solvers.py
+++ b/dedalus/core/solvers.py
@@ -99,7 +99,7 @@ def solve_dense(self, pencil, rebuild_coeffs=False, normalize_left=False, **kw):
             cacheid = None
         pencil.build_matrices(self.problem, ['M', 'L'], cacheid=cacheid)
         # Solve as dense general eigenvalue problem
-        eig_output = eig(pencil.L_exp.A, b=-pencil.M_exp.A, **kw)
+        eig_output = eig(pencil.L_exp.toarray(), b=-pencil.M_exp.toarray(), **kw)
         # Unpack output
         if len(eig_output) == 2:
             self.eigenvalues, self.eigenvectors = eig_output