diff --git a/lib/minixST/descr b/lib/minixST/descr
index acd9a5439..771918938 100644
--- a/lib/minixST/descr
+++ b/lib/minixST/descr
@@ -11,7 +11,7 @@ var LIB=lib/{M}/tail_
 var RT=lib/{M}/head_
 var MRT=lib/minixST/head_
 var MLIB=lib/minixST/tail_
-var CPP_F=-Dunix -DATARI_ST
+var CPP_F=-Dunix -DATARI_ST -DACK
 var INCLUDES=-I{EM}/lib/minixST/include -I{EM}/include/_tail_cc
 var ALIGN=-a0:4 -a1:4 -a2:4 -a3:4
 name be