diff --git a/src/xpra/scripts/main.py b/src/xpra/scripts/main.py
index d3e36e6e1a..cfff777162 100755
--- a/src/xpra/scripts/main.py
+++ b/src/xpra/scripts/main.py
@@ -2117,6 +2117,8 @@ def run_remote_server(error_cb, opts, args, mode, defaults):
         sns = {
                "start"          : start,
                "start-child"    : start_child,
+               "mode"           : mode,
+               "display"        : params.get("display", ""),
                }
         for x in ("exit-with-children", "exit-with-client",
                   "session-name", "encoding", "socket-dir", "dpi",
@@ -2209,7 +2211,7 @@ def start_server_subprocess(script_file, args, mode, defaults, dotxpra,
     #we must use a subprocess to avoid messing things up - yuk
     assert mode in ("start", "start-desktop", "shadow")
     existing_sockets = set()
-    if mode in ("start", "start_desktop"):
+    if mode in ("start", "start-desktop"):
         if len(args)==1:
             display_name = args[0]
         elif len(args)==0:
diff --git a/src/xpra/server/proxy/proxy_server.py b/src/xpra/server/proxy/proxy_server.py
index c4f4277346..81dd22c95b 100644
--- a/src/xpra/server/proxy/proxy_server.py
+++ b/src/xpra/server/proxy/proxy_server.py
@@ -21,7 +21,7 @@
 authlog = Logger("proxy", "auth")
 
 
-from xpra.util import LOGIN_TIMEOUT, AUTHENTICATION_ERROR, SESSION_NOT_FOUND, repr_ellipsized, print_nested_dict, csv, typedict
+from xpra.util import LOGIN_TIMEOUT, AUTHENTICATION_ERROR, SESSION_NOT_FOUND, SERVER_ERROR, repr_ellipsized, print_nested_dict, csv, typedict
 from xpra.server.proxy.proxy_instance_process import ProxyInstanceProcess
 from xpra.server.server_core import ServerCore
 from xpra.server.control_command import ArgsControlCommand, ControlError
@@ -217,17 +217,30 @@ def disconnect(reason, *extras):
         if len(displays)==0 or sns:
             if self._start_sessions:
                 #start a new session
+                mode = sns.get("mode", "start")
+                assert mode in ("start", "start-desktop", "shadow"), "invalid start-new-session mode '%s'" % mode
                 sns = typedict(sns)
                 from xpra.platform.dotxpra import DotXpra
                 dotxpra = DotXpra(opts.socket_dir, opts.socket_dirs)
+                args = []
+                display = sns.get("display")
+                if display:
+                    args = [display]
                 start = sns.strlistget("start")
                 start_child = sns.strlistget("start-child")
                 exit_with_children = sns.boolget("exit-with-children")
                 exit_with_client = sns.boolget("exit-with-client")
-                log("starting new server subprocess: start=%s, start-child=%s, exit-with-children=%s, exit-with-client=%s", start, start_child, exit_with_children, exit_with_client)
-                proc, display = start_server_subprocess(sys.argv[0], [], "start", opts, dotxpra,
-                                                        start, start_child,
-                                                        exit_with_children, exit_with_client)
+                log("starting new server subprocess: mode=%s, start=%s, start-child=%s, exit-with-children=%s, exit-with-client=%s", mode, start, start_child, exit_with_children, exit_with_client)
+                try:
+                    proc, display = start_server_subprocess(sys.argv[0], args, mode, opts, dotxpra,
+                                                            start, start_child,
+                                                            exit_with_children, exit_with_client)
+                except Exception as e:
+                    log("start_server_subprocess failed", exc_info=True)
+                    log.error("Error: failed to start server subprocess:")
+                    log.error(" %s", e)
+                    disconnect(SERVER_ERROR, "failed to start a new session")
+                    return
                 if proc:
                     self.child_reaper.add_process(proc, "server-%s" % display, "xpra start", True, True)
             else: