diff --git a/src/Quantity/Quantity_Color_1.hxx b/src/Quantity/Quantity_Color_1.hxx
index a14b13ad2b..e5d614a1dd 100644
--- a/src/Quantity/Quantity_Color_1.hxx
+++ b/src/Quantity/Quantity_Color_1.hxx
@@ -15,6 +15,8 @@
 #ifndef COLOR_PXX_INCLUDED
 #define COLOR_PXX_INCLUDED
 
+#include <Quantity_Parameter.hxx>
+
 #define RGBHLS_H_UNDEFINED -1.0
 
 static Quantity_Parameter TheEpsilon = 0.0001;