diff --git a/sys/kern/makesyscalls.sh b/sys/kern/makesyscalls.sh
index 5781d314c4c..7e1d63b5cca 100644
--- a/sys/kern/makesyscalls.sh
+++ b/sys/kern/makesyscalls.sh
@@ -42,6 +42,7 @@ cat_sysproto=""
 for stdc in ${stdcompat}; do
 	lowprefix=$(echo $stdc | tr '[[:upper:]]' '[[:lower:]]')
 	compatflag=$(echo $stdc | sed 's/FREEBSD/COMPAT/')
+	compatnum=$(echo $stdc | sed 's/FREEBSD//')
 	lowcompat=$(echo $compatflag | tr '[[:upper:]]' '[[:lower:]]')
 	sysent="sysent.$stdc.$$"
 	sysentdcl="sysent.${stdc}cl.$$"
@@ -68,7 +69,10 @@ for stdc in ${stdcompat}; do
 	conditional_compatcheck="$conditional_compatcheck type(\"$compatflag\")"
 
 	section_compatflagged="$section_compatflagged else if (flag(\"$compatflag\")) {
-		n$lowcompat++
+		if (mincompat > $compatnum)
+			is_obsol = 1
+		else
+			n$lowcompat++
 		out = \"$sysent\"
 		outdcl = \"$sysentdcl\"
 		wrap = \"$lowcompat\"
@@ -90,6 +94,7 @@ for stdc in ${stdcompat}; do
 	"
 done
 
+mincompat="0"
 sysent="sysent.switch.$$"
 sysinc="sysinc.switch.$$"
 sysarg="sysarg.switch.$$"
@@ -174,6 +179,7 @@ sed -e '
 		switchname = \"$switchname\"
 		namesname = \"$namesname\"
 		infile = \"$1\"
+		mincompat = \"$mincompat\" + 0
 		abi_func_prefix = \"$abi_func_prefix\"
 		capenabled_string = \"$capenabled\"
 		"'
@@ -589,9 +595,13 @@ sed -e '
 		syscall++
 		next
 	}
+	is_obsol = 0
 	type("COMPAT") || '" $conditional_compatcheck "' {
 		if (flag("COMPAT")) {
-			ncompat++
+			if (mincompat >= 4)
+				is_obsol = 1
+			else
+				ncompat++
 			out = syscompat
 			outdcl = syscompatdcl
 			wrap = "compat"
@@ -599,6 +609,18 @@ sed -e '
 			descr = "old"
 		} '" $section_compatflagged "'
 		parseline()
+		if (is_obsol) {
+			printf("\t{ 0, (sy_call_t *)nosys, AUE_NULL, NULL, 0, 0, 0, SY_THR_ABSENT },") > sysent
+			align_sysent_comment(34)
+			printf("/* %d = obsolete %s%s */\n", syscall,
+			    prefix, funcalias) > sysent
+			printf("\t\"obs_%s%s\",\t\t\t/* %d = obsolete %s%s */\n",
+			    prefix, funcalias, syscall, prefix, funcalias) > sysnames
+			printf("\t\t\t\t/* %d is obsolete %s%s */\n",
+			    syscall, prefix, funcalias) > syshdr
+			syscall++
+			next
+		}
 		if (argc != 0 && !flag("NOARGS") && !flag("NOPROTO") && \
 		    !flag("NODEF")) {
 			printf("struct %s {\n", argalias) > out