diff --git a/include/teqp/derivs.hpp b/include/teqp/derivs.hpp
index f9a5f166f801a1e3a682c84e88e9c756bae235a0..59abe582cb3f58beb75be5bdf37ccbf2999ba374 100644
--- a/include/teqp/derivs.hpp
+++ b/include/teqp/derivs.hpp
@@ -35,4 +35,10 @@ deriv3(const FuncType& f, TType T, const ContainerType& rho) {
 	rhocom[0] = comtype(rho[0], 0.0);
 	rhocom[1] = comtype(rho[1], h);
 	return f(T, rhocom).imag() / h;
+}
+
+template<typename Model, typename TType, typename RhoType>
+auto build_Psir_Hessian(const Model& model, const TType T, const RhoType& rho) {
+	// Double derivatives in each component's concentration
+
 }
\ No newline at end of file
diff --git a/include/teqp/eos.hpp b/include/teqp/eos.hpp
index dc63b3a246620cb4be0aaee7bf2240249ddc7373..b30b9f8289999285704b4b2130540130f9789874 100644
--- a/include/teqp/eos.hpp
+++ b/include/teqp/eos.hpp
@@ -91,10 +91,4 @@ public:
 		RhoType::value_type rhotot_ = (rhotot.has_value()) ? rhotot.value() : std::accumulate(std::begin(rho), std::end(rho), (RhoType::value_type)0.0);
 		return alphar(T, rho, rhotot_) * R * T * rhotot_;
 	}
-};
-
-template<typename Model, typename TType, typename RhoType>
-auto build_Psir_Hessian(const Model& model, const TType T, const RhoType& rho) {
-	// Double derivatives in each component's concentration
-
-}
\ No newline at end of file
+};
\ No newline at end of file