diff --git a/Exec/science/wdmerger/problem_initialize_state_data.H b/Exec/science/wdmerger/problem_initialize_state_data.H
index 85b9975d54..747f8442c4 100644
--- a/Exec/science/wdmerger/problem_initialize_state_data.H
+++ b/Exec/science/wdmerger/problem_initialize_state_data.H
@@ -70,13 +70,21 @@ void problem_initialize_state_data (int i, int j, int k,
                          loc[1] - problem::center_P_initial[1],
                          loc[2] - problem::center_P_initial[2]};
 
-        auto rho_P = interpolate_3d(pos_P, dx, model::idens, problem::nsub, 0);
+        double rho_P{0.0};
+
+        if (problem::mass_P > 0.0_rt) {
+            rho_P = interpolate_3d(pos_P, dx, model::idens, problem::nsub, 0);
+        }
 
         Real pos_S[3] = {loc[0] - problem::center_S_initial[0],
                          loc[1] - problem::center_S_initial[1],
                          loc[2] - problem::center_S_initial[2]};
 
-        auto rho_S = interpolate_3d(pos_S, dx, model::idens, problem::nsub, 1);
+        double rho_S{0.0};
+
+        if (problem::mass_S > 0.0_rt) {
+            rho_S = interpolate_3d(pos_S, dx, model::idens, problem::nsub, 1);
+        }
 
         if (rho_P > rho_S) {
             // use the primary star initialization