diff --git a/src/test/unit/mcmc/hmc/integrators/expl_leapfrog_test.cpp b/src/test/unit/mcmc/hmc/integrators/expl_leapfrog_test.cpp
index 4c2873033ad..9152cc47280 100644
--- a/src/test/unit/mcmc/hmc/integrators/expl_leapfrog_test.cpp
+++ b/src/test/unit/mcmc/hmc/integrators/expl_leapfrog_test.cpp
@@ -417,7 +417,9 @@ TEST_F(McmcHmcIntegratorsExplLeapfrogF, evolve_9) {
   z.q(0) = 1.27097196280777;
   z.p(0) = -0.159996782671291;
   z.g(0) = 1.27097196280777;
-  z.get_inv_metric()(0) = 0.733184698671436;
+  Eigen::VectorXd inv_metric(1);
+  inv_metric << 0.733184698671436;
+  z.set_inv_metric(inv_metric);
   EXPECT_NEAR(z.V, 0.807684865121721, 1e-15);
   EXPECT_NEAR(z.q(0), 1.27097196280777, 1e-15);
   EXPECT_NEAR(z.p(0), -0.159996782671291, 1e-15);