diff --git a/gtsam/linear/GaussianBayesNet.cpp b/gtsam/linear/GaussianBayesNet.cpp
index 41a734b34..229d4a932 100644
--- a/gtsam/linear/GaussianBayesNet.cpp
+++ b/gtsam/linear/GaussianBayesNet.cpp
@@ -64,8 +64,9 @@ namespace gtsam {
     return sample(result, rng);
   }
 
-  VectorValues GaussianBayesNet::sample(VectorValues result,
+  VectorValues GaussianBayesNet::sample(const VectorValues& given,
                                         std::mt19937_64* rng) const {
+    VectorValues result(given);
     // sample each node in reverse topological sort order (parents first)
     for (auto cg : boost::adaptors::reverse(*this)) {
       const VectorValues sampled = cg->sample(result, rng);
@@ -79,7 +80,7 @@ namespace gtsam {
     return sample(&kRandomNumberGenerator);
   }
 
-  VectorValues GaussianBayesNet::sample(VectorValues given) const {
+  VectorValues GaussianBayesNet::sample(const VectorValues& given) const {
     return sample(given, &kRandomNumberGenerator);
   }
 
diff --git a/gtsam/linear/GaussianBayesNet.h b/gtsam/linear/GaussianBayesNet.h
index 83328576f..e81d6af33 100644
--- a/gtsam/linear/GaussianBayesNet.h
+++ b/gtsam/linear/GaussianBayesNet.h
@@ -110,13 +110,13 @@ namespace gtsam {
      *   VectorValues given = ...;
      *   auto sample = gbn.sample(given, &rng);
      */
-    VectorValues sample(VectorValues given, std::mt19937_64* rng) const;
+    VectorValues sample(const VectorValues& given, std::mt19937_64* rng) const;
 
     /// Sample using ancestral sampling, use default rng
     VectorValues sample() const;
 
     /// Sample from an incomplete BayesNet, use default rng
-    VectorValues sample(VectorValues given) const;
+    VectorValues sample(const VectorValues& given) const;
 
     /**
      * Return ordering corresponding to a topological sort.