diff --git a/lib/sl/sl.h b/lib/sl/sl.h
index edaa0456d..ab9fc890b 100644
--- a/lib/sl/sl.h
+++ b/lib/sl/sl.h
@@ -50,11 +50,11 @@ struct sl_cmd {
 typedef struct sl_cmd SL_cmd;
 
 void sl_help (SL_cmd *, int argc, char **argv);
-int  sl_loop (SL_cmd *, char *prompt);
-int  sl_command_loop (SL_cmd *cmds, char *prompt, void **data);
+int  sl_loop (SL_cmd *, const char *prompt);
+int  sl_command_loop (SL_cmd *cmds, const char *prompt, void **data);
 int  sl_command (SL_cmd *cmds, int argc, char **argv);
 int sl_make_argv(char*, int*, char***);
-void sl_apropos (SL_cmd *cmd, char *topic);
+void sl_apropos (SL_cmd *cmd, const char *topic);
 
 
 #endif /* _SL_H */