diff --git a/inst/include/nsoptim/optimizer/mm.hpp b/inst/include/nsoptim/optimizer/mm.hpp
index c3ba656fd9349a51b289bc952741034e3ef35e91..4f3c8c03f1d87fb5005d1e39ef2ff8315a71e2eb 100644
--- a/inst/include/nsoptim/optimizer/mm.hpp
+++ b/inst/include/nsoptim/optimizer/mm.hpp
@@ -438,7 +438,8 @@ class MMOptimizer : public Optimizer<LossFunction, PenaltyFunction, Coefficients
       // Compute the minimizer of the convex surrogates.
       auto optimum = optimizer_.Optimize();
       if (optimum.metrics) {
-        metrics->AddSubMetrics(*optimum.metrics);
+        metrics->AddSubMetrics(std::move(*optimum.metrics));
+        optimum.metrics.reset();
       }
 
       // Check for any problems.