diff --git a/lib/i86/descr b/lib/i86/descr
index 0d795805..cbf6efb7 100644
--- a/lib/i86/descr
+++ b/lib/i86/descr
@@ -9,7 +9,7 @@ var NAME=i86
 var M=i86
 var LIB=lib/{M}/tail_
 var RT=lib/{M}/head_
-var CPP_F=-Dunix
+var CPP_F=-Dunix -D__USG
 var INCLUDES=-I{EM}/include/_tail_cc
 var ALIGN=-a0:2 -a1:2 -a2:2 -a3:2
 name be
diff --git a/lib/m68020/descr b/lib/m68020/descr
index 1102aef0..2d0731fb 100644
--- a/lib/m68020/descr
+++ b/lib/m68020/descr
@@ -9,7 +9,7 @@ var NAME=m68020
 var M=m68020
 var LIB=lib/{M}/tail_
 var RT=lib/{M}/head_
-var CPP_F=-Dunix=unix
+var CPP_F=-Dunix=unix -D__USG
 var INCLUDES=-I{EM}/include/_tail_cc
 # 410 align is the default
 var ALIGN=-a0:2 -a1:2 -a2:0x10000 -a3:2
diff --git a/lib/mantra/descr b/lib/mantra/descr
index a15d692e..d80f92e7 100644
--- a/lib/mantra/descr
+++ b/lib/mantra/descr
@@ -11,7 +11,7 @@ var LIB=lib/{M}/tail_
 var RT=lib/{M}/head_
 var NLIB=lib/mantra/tail_
 var NRT=lib/mantra/head_
-var CPP_F=-Dunix=unix -Dm68000=m68000
+var CPP_F=-Dunix=unix -D__USG
 var INCLUDES=-I{EM}/include/_tail_cc
 # 407 align is the default
 var ALIGN=-a0:2 -a1:2 -a2:2 -a3:2