diff --git a/mach/vax4/libbc/Makefile b/mach/vax4/libbc/Makefile
index 4a2432c59..1573b6da0 100644
--- a/mach/vax4/libbc/Makefile
+++ b/mach/vax4/libbc/Makefile
@@ -1,5 +1,6 @@
+SUF=o
 MAKEFILE=../../proto/libg/Makefile
-MACHDEF="MACH=vax4" "SUF=o" "ASAR=ar"
+MACHDEF="MACH=vax4" "SUF=$(SUF)" "ASAR=ar"
 BCDEF="PREF=bc" "SUB=" "SRC=lang/basic/lib"
 
 install:
diff --git a/mach/vax4/libcc/Makefile b/mach/vax4/libcc/Makefile
index cb00adb8b..43ce0a411 100644
--- a/mach/vax4/libcc/Makefile
+++ b/mach/vax4/libcc/Makefile
@@ -1,5 +1,6 @@
+SUF=o
 MAKEFILE=../../proto/libg/Makefile
-MACHDEF="MACH=vax4" "SUF=o" "ASAR=ar"
+MACHDEF="MACH=vax4" "SUF=$(SUF)" "ASAR=ar"
 STDIO="PREF=cc" "SUB=.1s" "SRC=lang/cem/libcc/stdio"
 GEN="PREF=cc" "SUB=.2g" "SRC=lang/cem/libcc/gen"
 MON="PREF=mon" "SRC=lang/cem/libcc/mon"
diff --git a/mach/vax4/libpc/Makefile b/mach/vax4/libpc/Makefile
index 9fbb701a0..c22795d0e 100644
--- a/mach/vax4/libpc/Makefile
+++ b/mach/vax4/libpc/Makefile
@@ -1,5 +1,6 @@
+SUF=o
 MAKEFILE=../../proto/libg/Makefile
-MACHDEF="MACH=vax4" "SUF=o" "ASAR=ar"
+MACHDEF="MACH=vax4" "SUF=$(SUF)" "ASAR=ar"
 PCDEF="PREF=pc" "SUB=" "SRC=lang/pc/libpc"
 
 install: