diff --git a/basis/command.lua b/basis/command.lua
index a7f15db..584adbe 100644
--- a/basis/command.lua
+++ b/basis/command.lua
@@ -339,6 +339,19 @@ function techage.not_protected(number, placer_name, clicker_name)
 	return false
 end
 
+-- Check the given number value.
+-- Returns true if the number is valid, point to real node and
+-- and the node is not protected for the given player_name.
+function techage.check_number(number, placer_name)
+	if number then
+		if not techage.not_protected(number, placer_name, nil) then
+			return false
+		end
+		return true
+	end
+	return false
+end
+
 -- Check the given list of numbers.
 -- Returns true if number(s) is/are valid, point to real nodes and
 -- and the nodes are not protected for the given player_name.
diff --git a/move_controller/movecontroller.lua b/move_controller/movecontroller.lua
index be1bb5d..caf29af 100644
--- a/move_controller/movecontroller.lua
+++ b/move_controller/movecontroller.lua
@@ -40,7 +40,7 @@ local WRENCH_MENU = {
 		label = S("Handover to B"),
 		tooltip = S("Number of the next movecontroller"),
 		default = "",
-		check = techage.check_numbers,
+		check = techage.check_number,
 	},
 	{
 		type = "number",
@@ -48,7 +48,7 @@ local WRENCH_MENU = {
 		label = S("Handover to A"),
 		tooltip = S("Number of the previous movecontroller"),
 		default = "",
-		check = techage.check_numbers,
+		check = techage.check_number,
 	},
 	{
 		type = "float",