diff --git a/extra/unix/unix.factor b/extra/unix/unix.factor
index 9a7d405546..4583905833 100755
--- a/extra/unix/unix.factor
+++ b/extra/unix/unix.factor
@@ -26,6 +26,8 @@ TYPEDEF: uint socklen_t
 : ESRCH 3 ; inline
 : EEXIST 17 ; inline
 
+: NGROUPS_MAX 16 ; inline
+
 C-STRUCT: group
     { "char*" "gr_name" }
     { "char*" "gr_passwd" }