diff --git a/test_problems/ChemEquil_gri_matrix/gri_matrix.cpp b/test_problems/ChemEquil_gri_matrix/gri_matrix.cpp
index 121e4a595..8b016a734 100644
--- a/test_problems/ChemEquil_gri_matrix/gri_matrix.cpp
+++ b/test_problems/ChemEquil_gri_matrix/gri_matrix.cpp
@@ -13,6 +13,7 @@
 
 using namespace std;
 using namespace Cantera;
+using namespace Cantera_CXX;
 
 int main(int argc, char **argv) {
   int numSucc = 0;