diff --git a/src/CoolProp.i b/src/CoolProp.i
index cd5e5216..89f1e92f 100644
--- a/src/CoolProp.i
+++ b/src/CoolProp.i
@@ -46,10 +46,12 @@ namespace std {
 #define SWIG
 #include "Configuration.h"
 #undef SWIG
+#include "HumidAirProp.h"
 %}
 
 %include "DataStructures.h"
 %include "AbstractState.h"
 %include "CoolProp.h"
 %include "PhaseEnvelope.h"
-%include "Configuration.h"
\ No newline at end of file
+%include "Configuration.h"
+%include "HumidAirProp.h"
\ No newline at end of file