diff --git a/include/teqp/derivs.hpp b/include/teqp/derivs.hpp
index 5954d74..005d196 100644
--- a/include/teqp/derivs.hpp
+++ b/include/teqp/derivs.hpp
@@ -259,6 +259,7 @@ struct TDXDerivatives {
     }
     
     #define get_ATrhoXi_runtime_combinations \
+        X(0,0,0) \
         X(0,0,1) \
         X(0,0,2) \
         X(0,0,3) \