diff --git a/data/login.d/02sddm b/data/login.d/02sddm
new file mode 100644
index 0000000..5926d9b
--- /dev/null
+++ b/data/login.d/02sddm
@@ -0,0 +1,30 @@
+#! /bin/sh
+# Copyright 2015 Calculate Ltd. http://www.calculate-linux.org
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+
+run_script() {
+	# drop second X session for sddm
+	local online="$(desktop_variable_value desktop.cl_desktop_online_user)"
+	if [[ $XAUTHORITY =~ /sddm/ ]] && [[ "$online" =~ (^|,)$USER(,|$) ]]
+	then
+		local message="A second X session cannot be opened for user $USER."
+		if type kdialog
+		then
+			kdialog --error "$message"
+		else
+			xmes "$message"
+		fi
+		exit 1
+	fi
+}
diff --git a/setup.py b/setup.py
index d19f554..83ca9db 100755
--- a/setup.py
+++ b/setup.py
@@ -73,6 +73,7 @@ data_files = [('/usr/share/calculate/xdm', [('data/cmd_login', 0755),
                                              ('data/setbg', 0755)]),
               ('/usr/share/calculate/xdm/login.d',
                                             ['data/login.d/00init',
+                                             'data/login.d/02sddm',
                                              'data/login.d/05fast_login',
                                              'data/login.d/20desktop',
                                              'data/login.d/99final']),