diff -up a/slock.c b/slock.c
--- a/slock.c	2026-07-28 03:28:03.120285888 +0530
+++ b/slock.c	2026-08-03 11:20:35.223992495 +0530
@@ -6,7 +6,9 @@
 
 #include <ctype.h>
 #include <errno.h>
+#include <fcntl.h>
 #include <grp.h>
+#include <limits.h>
 #include <pwd.h>
 #include <stdarg.h>
 #include <stdlib.h>
@@ -59,7 +61,6 @@ die(const char *errstr, ...)
 }
 
 #ifdef __linux__
-#include <fcntl.h>
 #include <linux/oom.h>
 
 static void
@@ -301,6 +302,28 @@ lockscreen(Display *dpy, struct xrandr *
 	return NULL;
 }
 
+static int
+get_xss_sleep_lock_fd(void)
+{
+	char *env_str, *end;
+	long env_val;
+
+	env_str = getenv("XSS_SLEEP_LOCK_FD");
+	if (!env_str || !*env_str)
+		return -1;
+
+	errno = 0;
+	env_val = strtol(env_str, &end, 10);
+	if (errno ||
+	    *end ||
+	    (env_val < 0 || env_val > INT_MAX)) {
+		fprintf(stderr, "slock: strtol $XSS_SLEEP_LOCK_FD: %s\n",
+		        errno ? strerror(errno) : "invalid value");
+		return -1;
+	}
+	return (int)env_val;
+}
+
 static void
 usage(void)
 {
@@ -318,6 +341,7 @@ main(int argc, char **argv) {
 	const char *hash;
 	Display *dpy;
 	int s, nlocks, nscreens;
+	int lockfd;
 
 	ARGBEGIN {
 	case 'v':
@@ -327,6 +351,18 @@ main(int argc, char **argv) {
 		usage();
 	} ARGEND
 
+	lockfd = get_xss_sleep_lock_fd();
+	if (lockfd >= 0) {
+		int flags = fcntl(lockfd, F_GETFD);
+		if (flags < 0) {
+			fprintf(stderr, "slock: fcntl $XSS_SLEEP_LOCK_FD F_GETFD: %s\n",
+			        strerror(errno));
+		} else if (fcntl(lockfd, F_SETFD, flags | FD_CLOEXEC) == -1) {
+			fprintf(stderr, "slock: fcntl $XSS_SLEEP_LOCK_FD F_SETFD: %s\n",
+			        strerror(errno));
+		}
+	}
+
 	/* validate drop-user and -group */
 	errno = 0;
 	if (!(pwd = getpwnam(user)))
@@ -378,6 +414,9 @@ main(int argc, char **argv) {
 	if (nlocks != nscreens)
 		return 1;
 
+	if (lockfd >= 0 && close(lockfd) < 0)
+		fprintf(stderr, "slock: close $XSS_SLEEP_LOCK_FD: %s\n", strerror(errno));
+
 	/* run post-lock command */
 	if (argc > 0) {
 		pid_t pid;