diff --git a/test_problems/ChemEquil_ionizedGas/ionizedGasEquil.cpp b/test_problems/ChemEquil_ionizedGas/ionizedGasEquil.cpp
index 7f0a43ab2..bcfa933b6 100644
--- a/test_problems/ChemEquil_ionizedGas/ionizedGasEquil.cpp
+++ b/test_problems/ChemEquil_ionizedGas/ionizedGasEquil.cpp
@@ -20,6 +20,8 @@
 
 using namespace std;
 using namespace Cantera;
+using namespace Cantera_CXX;
+
 int main(int argc, char **argv) {
 #ifdef DEBUG_CHEMEQUIL
   ChemEquil_print_lvl = 0;