diff --git a/tree/.local/bin/screenlock.tpl b/tree/.local/bin/screenlock.tpl
index 7f37817..bdb918d 100755
--- a/tree/.local/bin/screenlock.tpl
+++ b/tree/.local/bin/screenlock.tpl
@@ -27,6 +27,13 @@ echo "screenlock not configured for this system"
 exit 1
 {% end %}
 
+
+# check if lock program is running
+if ps -e | grep " $LOCKPROG$"; then
+	echo "$LOCKPROG is already running!"
+	exit 1
+fi
+
 for CMD in $OPTIONAL_CMDS; do
 	if ! command -v "$CMD" &> /dev/null
 	then