diff --git a/src/string_func.h b/src/string_func.h
--- a/src/string_func.h
+++ b/src/string_func.h
@@ -95,7 +95,7 @@ char *CDECL str_fmt(const char *str, ...
 
 /** Scans the string for valid characters and if it finds invalid ones,
  * replaces them with a question mark '?' */
-void str_validate(char *str);
+void str_validate(char *str, bool allow_newlines = false);
 
 /** Scans the string for colour codes and strips them */
 void str_strip_colours(char *str);