diff --git a/tests/sys/kern/kern_descrip_test.c b/tests/sys/kern/kern_descrip_test.c
index 59a81630786e..6953b00fc6f2 100644
--- a/tests/sys/kern/kern_descrip_test.c
+++ b/tests/sys/kern/kern_descrip_test.c
@@ -29,22 +29,31 @@ __FBSDID("$FreeBSD$");
 
 #include <errno.h>
 #include <fcntl.h>
+#include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <strings.h>
 #include <sys/limits.h>
 #include <sys/stat.h>
+#include <sys/sysctl.h>
 #include <unistd.h>
 #include <atf-c.h>
 
-ATF_TC_WITHOUT_HEAD(dup2_simple);
-ATF_TC_BODY(dup2_simple, tc)
+static volatile sig_atomic_t done;
+
+#define AFILE "afile"
+#define EXPANDBY 1000
+#define PARALLEL 4
+#define RENDEZVOUS "rendezvous"
+#define VALUE "value"
+
+ATF_TC_WITHOUT_HEAD(dup2__simple);
+ATF_TC_BODY(dup2__simple, tc)
 {
 	int fd1, fd2;
 	struct stat sb1, sb2;
 
-	fd1 = open("/etc/passwd", O_RDONLY);
-	ATF_REQUIRE(fd1 >= 0);
+	ATF_REQUIRE((fd1 = open(AFILE, O_CREAT, 0644)) != -1);
 	fd2 = 27;
 	ATF_REQUIRE(dup2(fd1, fd2) != -1);
 	ATF_REQUIRE(fstat(fd1, &sb1) != -1);
@@ -57,22 +66,125 @@ ATF_TC_HEAD(dup2__ebadf_when_2nd_arg_out_of_range, tc)
 {
 	atf_tc_set_md_var(tc, "descr", "Regression test for r234131");
 }
+
 ATF_TC_BODY(dup2__ebadf_when_2nd_arg_out_of_range, tc)
 {
 	int fd1, fd2, ret;
 
-	fd1 =  open("/etc/passwd", O_RDONLY);
+	ATF_REQUIRE((fd1 = open(AFILE, O_CREAT, 0644)) != -1);
 	fd2 = INT_MAX;
 	ret = dup2(fd1, fd2);
 	ATF_CHECK_EQ(-1, ret);
 	ATF_CHECK_EQ(EBADF, errno);
 }
 
+static void
+handler(int s __unused)
+{
+	done++;
+}
+
+static void
+openfiles2(size_t n)
+{
+	size_t i;
+	int r;
+
+	errno = 0;
+	for (i = 0; i < n; i++)
+		ATF_REQUIRE((r = open(AFILE, O_RDONLY)) != -1);
+	kill(getppid(), SIGUSR1);
+
+	for (;;) {
+		if (access(RENDEZVOUS, R_OK) != 0)
+			break;
+		usleep(1000);
+	}
+	_exit(0);
+}
+
+static void
+openfiles(size_t n)
+{
+	int i, fd;
+
+	signal(SIGUSR1, handler);
+	ATF_REQUIRE((fd = open(AFILE, O_CREAT, 0644)) != -1);
+	close(fd);
+	ATF_REQUIRE((fd = open(RENDEZVOUS, O_CREAT, 0644)) != -1);
+	close(fd);
+	done = 0;
+	for (i = 0; i < PARALLEL; i++)
+		if (fork() == 0)
+			openfiles2(n / PARALLEL);
+	while (done != PARALLEL)
+		usleep(1000);
+	unlink(RENDEZVOUS);
+	usleep(40000);
+}
+
+ATF_TC_WITH_CLEANUP(kern_maxfiles__increase);
+ATF_TC_HEAD(kern_maxfiles__increase, tc)
+{
+	atf_tc_set_md_var(tc, "require.user", "root");
+	atf_tc_set_md_var(tc, "require.config", "allow_sysctl_side_effects");
+	atf_tc_set_md_var(tc, "descr",
+	    "Check kern.maxfiles expansion");
+}
+
+ATF_TC_BODY(kern_maxfiles__increase, tc)
+{
+	size_t oldlen;
+	int maxfiles, oldmaxfiles, current;
+	char buf[80];
+
+	oldlen = sizeof(maxfiles);
+	if (sysctlbyname("kern.maxfiles", &maxfiles, &oldlen, NULL, 0) == -1)
+		atf_tc_fail("getsysctlbyname(%s): %s", "kern.maxfiles",
+		    strerror(errno));
+	if (sysctlbyname("kern.openfiles", &current, &oldlen, NULL, 0) == -1)
+		atf_tc_fail("getsysctlbyname(%s): %s", "kern.openfiles",
+		    strerror(errno));
+
+	oldmaxfiles = maxfiles;
+
+	/* Store old kern.maxfiles in a symlink for cleanup */
+	snprintf(buf, sizeof(buf), "%d", oldmaxfiles);
+	if (symlink(buf, VALUE) == 1)
+		atf_tc_fail("symlink(%s, %s): %s", buf, VALUE,
+		    strerror(errno));
+
+	maxfiles += EXPANDBY;
+	if (sysctlbyname("kern.maxfiles", NULL, 0, &maxfiles, oldlen) == -1)
+		atf_tc_fail("getsysctlbyname(%s): %s", "kern.maxfiles",
+		    strerror(errno));
+
+	openfiles(oldmaxfiles - current + 1);
+	(void)unlink(VALUE);
+}
+
+ATF_TC_CLEANUP(kern_maxfiles__increase, tc)
+{
+	size_t oldlen;
+	int n, oldmaxfiles;
+	char buf[80];
+
+	if ((n = readlink(VALUE, buf, sizeof(buf))) > 0) {
+		buf[n] = '\0';
+		if (sscanf(buf, "%d", &oldmaxfiles) == 1) {
+			oldlen = sizeof(oldmaxfiles);
+			(void) sysctlbyname("kern.maxfiles", NULL, 0,
+			    &oldmaxfiles, oldlen);
+		}
+	}
+}
+
 ATF_TP_ADD_TCS(tp)
 {
 
-        ATF_TP_ADD_TC(tp, dup2_simple);
-        ATF_TP_ADD_TC(tp, dup2__ebadf_when_2nd_arg_out_of_range);
+	ATF_TP_ADD_TC(tp, dup2__simple);
+	ATF_TP_ADD_TC(tp, dup2__ebadf_when_2nd_arg_out_of_range);
+	ATF_TP_ADD_TC(tp, kern_maxfiles__increase);
 
-        return atf_no_error();
+	return (atf_no_error());
 }