diff --git a/luprex/cpp/drv/readline.hpp b/luprex/cpp/drv/readline.hpp
index c439f0e4..0b98aaae 100644
--- a/luprex/cpp/drv/readline.hpp
+++ b/luprex/cpp/drv/readline.hpp
@@ -31,7 +31,6 @@ public:
     
     // change the prompt.
     void set_prompt(const CodepointString &prompt);
-    void set_prompt_utf8(const std::string &prompt);
 
     // Use this to print anything on the console.
     void print(const CodepointString &cps);