diff --git a/custrom_functions_you_can_override.lua b/custrom_functions_you_can_override.lua
index 52b23e6..f4e2153 100644
--- a/custrom_functions_you_can_override.lua
+++ b/custrom_functions_you_can_override.lua
@@ -38,7 +38,7 @@ yl_speak_up.replace_vars_in_text = function(text, dialog, pname)
 	-- substitutions in it using substring captured by "()" in
 	-- pattern. "[%a_]+" means one or more letter or underscore.
 	-- If lookup returns nil, then no substitution is made.
-	text = string.gsub(text, "%$([%a_]+)%$", subs)
+	text = string.gsub(text or "", "%$([%a_]+)%$", subs)
 
 	return text
 end