diff --git a/src/OpenFOAM/primitives/functions/Function1/Function1/Function1.C b/src/OpenFOAM/primitives/functions/Function1/Function1/Function1.C
index 0f8cb617c5..3157502db2 100644
--- a/src/OpenFOAM/primitives/functions/Function1/Function1/Function1.C
+++ b/src/OpenFOAM/primitives/functions/Function1/Function1/Function1.C
@@ -25,6 +25,8 @@ License
 
 #include "Function1.H"
 #include "Time.H"
+// Required by clang 5 for correct instantiation of Function1::New
+#include "Constant.H"
 
 // * * * * * * * * * * * * * * * * Constructor * * * * * * * * * * * * * * * //