diff --git a/config.h.in b/config.h.in
index dafe77090..7a0d44e66 100755
--- a/config.h.in
+++ b/config.h.in
@@ -152,5 +152,9 @@ typedef  int          ftnlen;       // Fortran hidden string length type
 
 #undef WITH_PRIME
 
+//    Enable the VCS NonIdeal equilibrium solver. This is
+//    accessed by specifying the solver=2 option
+#undef WITH_VCSNONIDEAL
+
 
 #endif