diff --git a/gtsam/base/tests/testGroup.cpp b/gtsam/base/tests/testGroup.cpp
index dadf2896c..241f71802 100644
--- a/gtsam/base/tests/testGroup.cpp
+++ b/gtsam/base/tests/testGroup.cpp
@@ -30,6 +30,7 @@ class Symmetric: private Eigen::PermutationMatrix<N> {
       Eigen::PermutationMatrix<N>(P) {
   }
 public:
+  static Symmetric identity() { return Symmetric(); }
   Symmetric() {
     Eigen::PermutationMatrix<N>::setIdentity();
   }