diff --git a/mach/vax4/libbsd4_2/LIST b/mach/vax4/libbsd4_2/LIST
index e98f7eff7..332c48953 100644
--- a/mach/vax4/libbsd4_2/LIST
+++ b/mach/vax4/libbsd4_2/LIST
@@ -29,6 +29,7 @@ _getrusage.s
 _lseek.s
 _sigblock.s
 _sigvec.s
+_sigsetmask.s
 accept.s
 access.s
 acct.s
diff --git a/mach/vax4/libbsd4_2/_sigsetmask.s b/mach/vax4/libbsd4_2/_sigsetmask.s
new file mode 100644
index 000000000..48cdc2c54
--- /dev/null
+++ b/mach/vax4/libbsd4_2/_sigsetmask.s
@@ -0,0 +1,3 @@
+#include "syscall.h"
+DEFINE(__sigsetmask)
+SYSTEM(SYS_sigsetmask)