diff --git a/src/xpra/platform/features.py b/src/xpra/platform/features.py
index 53ef38ee49..b001b31e4e 100644
--- a/src/xpra/platform/features.py
+++ b/src/xpra/platform/features.py
@@ -26,6 +26,8 @@
 CLIPBOARD_GREEDY = envbool("XPRA_CLIPBOARD_GREEDY")
 CLIPBOARD_NATIVE_CLASS = None
 
+EXECUTABLE_EXTENSION = ""
+
 UI_THREAD_POLLING = 0
 OPEN_COMMAND = []
 
@@ -69,6 +71,7 @@
                    "CLIPBOARD_WANT_TARGETS",
                    "CLIPBOARD_GREEDY",
                    "CLIPBOARD_NATIVE_CLASS",
+                   "EXECUTABLE_EXTENSION",
                    "UI_THREAD_POLLING",
                    "CLIENT_MODULES",
                    "INPUT_DEVICES",
diff --git a/src/xpra/platform/win32/features.py b/src/xpra/platform/win32/features.py
index a60fad75e6..d953da7abf 100644
--- a/src/xpra/platform/win32/features.py
+++ b/src/xpra/platform/win32/features.py
@@ -14,6 +14,8 @@
 CLIPBOARD_GREEDY = True
 CLIPBOARD_NATIVE_CLASS = "xpra.clipboard.translated_clipboard.TranslatedClipboardProtocolHelper"
 
+EXECUTABLE_EXTENSION = "exe"
+
 #these don't make sense on win32:
 DEFAULT_PULSEAUDIO_COMMAND = ""
 DEFAULT_PULSEAUDIO_CONFIGURE_COMMANDS = []
diff --git a/src/xpra/server/auth/exec_auth.py b/src/xpra/server/auth/exec_auth.py
index 25e82dfb19..fbba41e0ac 100644
--- a/src/xpra/server/auth/exec_auth.py
+++ b/src/xpra/server/auth/exec_auth.py
@@ -6,10 +6,10 @@
 import os
 from subprocess import Popen
 
-from xpra.os_util import POSIX
 from xpra.util import envint
 from xpra.child_reaper import getChildReaper
 from xpra.server.auth.sys_auth_base import SysAuthenticator, init, log
+from xpra.platform.features import EXECUTABLE_EXTENSION
 from xpra.gtk_common.gobject_compat import import_glib
 
 glib = import_glib()
@@ -24,9 +24,6 @@ class Authenticator(SysAuthenticator):
 
     def __init__(self, username, **kwargs):
         log("exec.Authenticator(%s, %s)", username, kwargs)
-        if not POSIX:
-            log.warn("Warning: exec authentication is not supported on %s", os.name)
-            return
         self.command = kwargs.pop("command", "")
         self.timeout = kwargs.pop("timeout", TIMEOUT)
         self.timer = None
@@ -37,9 +34,14 @@ def __init__(self, username, **kwargs):
             from xpra.platform.paths import get_libexec_dir
             libexec = get_libexec_dir()
             xpralibexec = os.path.join(libexec, "xpra")
+            log("libexec=%s, xpralibexec=%s", libexec, xpralibexec)
             if os.path.exists(xpralibexec):
                 libexec = xpralibexec
             auth_dialog = os.path.join(libexec, "auth_dialog")
+            if EXECUTABLE_EXTENSION:
+                #ie: add ".exe" on MS Windows
+                auth_dialog += ".%s" % EXECUTABLE_EXTENSION
+            log("auth_dialog=%s", auth_dialog)
             if os.path.exists(auth_dialog):
                 self.command = auth_dialog
         assert self.command, "exec authentication module is not configured correctly: no command specified"