diff --git a/tests/testSerializationSlam.cpp b/tests/testSerializationSlam.cpp
index bc2f5e864..3a1798f5e 100644
--- a/tests/testSerializationSlam.cpp
+++ b/tests/testSerializationSlam.cpp
@@ -614,6 +614,8 @@ static GaussianFactorGraph read(const string& name) {
 /* ************************************************************************* */
 // Read from XML file
 TEST(SubgraphSolver, Solves) {
+  using gtsam::example::planarGraph;
+  
   // Create preconditioner
   SubgraphPreconditioner system;