diff --git a/api/custom_functions_you_can_override.lua b/api/custom_functions_you_can_override.lua
index 0ad3cc7..d815b1e 100644
--- a/api/custom_functions_you_can_override.lua
+++ b/api/custom_functions_you_can_override.lua
@@ -514,6 +514,9 @@ yl_speak_up.custom_functions_r_[ "set_variable_to_random_number" ] = {
 		-- set the value of the variable
 		local n1 = tonumber(r.r_param2)
 		local n2 = tonumber(r.r_param3)
+		if(n1 == nil or n2 == nil) then
+			return false
+		end
 		if(n2 < n1) then
 			local tmp = n1
 			n1 = n2