diff --git a/include/teqp/models/multifluid.hpp b/include/teqp/models/multifluid.hpp
index 7c4f11194873dad31fb7697e8f91395ccec2624d..a02db5dd0eb5f55c903c69ad9b6994ba51b2e5d3 100644
--- a/include/teqp/models/multifluid.hpp
+++ b/include/teqp/models/multifluid.hpp
@@ -11,6 +11,7 @@
 
 #include "teqp/derivs.hpp"
 #include "teqp/types.hpp"
+#include "teqp/constants.hpp"
 
 #include "MultiComplex/MultiComplex.hpp"