diff --git a/unix/vncserver/vncsession.c b/unix/vncserver/vncsession.c
index c722922183..ba131fbd92 100644
--- a/unix/vncserver/vncsession.c
+++ b/unix/vncserver/vncsession.c
@@ -503,6 +503,14 @@ run_script(const char *username, const char *display, char **envp)
     _exit(EX_OSERR);
 }
 
+static void
+usage(void)
+{
+    fprintf(stderr, "Syntax:\n");
+    fprintf(stderr, "    vncsession [-D] <username> <display>\n");
+    exit(EX_USAGE);
+}
+
 int
 main(int argc, char **argv)
 {
@@ -511,14 +519,23 @@ main(int argc, char **argv)
 
     const char *username, *display;
 
-    if ((argc != 3) || (argv[2][0] != ':')) {
-        fprintf(stderr, "Syntax:\n");
-        fprintf(stderr, "    %s <username> <display>\n", argv[0]);
-        return EX_USAGE;
+    int opt, forking = 1;
+
+    while ((opt = getopt(argc, argv, "D")) != -1) {
+        switch (opt) {
+        case 'D':
+            forking = 0;
+            break;
+        default:
+            usage();
+        }
     }
 
-    username = argv[1];
-    display = argv[2];
+    if ((argc != optind + 2) || (argv[optind +1][0] != ':'))
+        usage();
+
+    username = argv[argc - 2];
+    display = argv[argc - 1];
 
     if (geteuid() != 0) {
         fprintf(stderr, "This program needs to be run as root!\n");
@@ -534,8 +551,10 @@ main(int argc, char **argv)
         return EX_OSERR;
     }
 
-    if (begin_daemon() == -1)
-        return EX_OSERR;
+    if (forking) {
+        if (begin_daemon() == -1)
+            return EX_OSERR;
+    }
 
     openlog("vncsession", LOG_PID, LOG_AUTH);
 
@@ -586,7 +605,8 @@ main(int argc, char **argv)
         fclose(f);
     }
 
-    finish_daemon();
+    if (forking)
+        finish_daemon();
 
     while (1) {
         int status;
diff --git a/unix/vncserver/vncsession.man.in b/unix/vncserver/vncsession.man.in
index 4efad41bc5..d52da10bf3 100644
--- a/unix/vncserver/vncsession.man.in
+++ b/unix/vncserver/vncsession.man.in
@@ -3,6 +3,7 @@
 vncsession \- start a VNC server
 .SH SYNOPSIS
 .B vncsession
+.RI [-D]
 .RI < username >
 .RI <: display# >
 .SH DESCRIPTION
@@ -16,6 +17,15 @@ appropriate options and starts a window manager on the VNC desktop.
 is rarely called directly and is normally started by the system service
 manager.
 
+.SH -D OPTION
+.B vncsession
+by default forks and detaches. If the -D option is used, it does not fork and
+detach. This option is provided for use with system service managers that
+require services to run in the foreground. This option is not intended for
+debugging in a login shell from a terminal or for running
+.B vncsession
+from a terminal as an ordinary user.
+
 .SH FILES
 Several VNC-related files are found in the directory $HOME/.vnc:
 .TP