diff --git a/test_problems/ChemEquil_gri_pairs/gri_pairs.cpp b/test_problems/ChemEquil_gri_pairs/gri_pairs.cpp
index ea3978a5e..ac6090ae3 100644
--- a/test_problems/ChemEquil_gri_pairs/gri_pairs.cpp
+++ b/test_problems/ChemEquil_gri_pairs/gri_pairs.cpp
@@ -20,6 +20,7 @@
 
 using namespace std;
 using namespace Cantera;
+using namespace Cantera_CXX;
 
 int main(int argc, char **argv) {
   try {