diff --git a/linenoise.c b/linenoise.c
index 28f0749..d0e3b0d 100644
--- a/linenoise.c
+++ b/linenoise.c
@@ -355,7 +355,7 @@
  * in order to add completion options given the input string when the
  * user typed <tab>. See the example.c source code for a very easy to
  * understand example. */
-void linenoiseAddCompletion(linenoiseCompletions *lc, char *str) {
+void linenoiseAddCompletion(linenoiseCompletions *lc, const char *str) {
     size_t len = strlen(str);
     char *copy, **cvec;
 
@@ -921,7 +921,7 @@
 
 /* Save the history in the specified file. On success 0 is returned
  * otherwise -1 is returned. */
-int linenoiseHistorySave(char *filename) {
+int linenoiseHistorySave(const char *filename) {
     FILE *fp = fopen(filename,"w");
     int j;
     
@@ -937,7 +937,7 @@
  *
  * If the file exists and the operation succeeded 0 is returned, otherwise
  * on error -1 is returned. */
-int linenoiseHistoryLoad(char *filename) {
+int linenoiseHistoryLoad(const char *filename) {
     FILE *fp = fopen(filename,"r");
     char buf[LINENOISE_MAX_LINE];
     
diff --git a/linenoise.h b/linenoise.h
index f28824d..b0a168e 100644
--- a/linenoise.h
+++ b/linenoise.h
@@ -44,13 +44,13 @@
 
 typedef void(linenoiseCompletionCallback)(const char *, linenoiseCompletions *);
 void linenoiseSetCompletionCallback(linenoiseCompletionCallback *);
-void linenoiseAddCompletion(linenoiseCompletions *, char *);
+void linenoiseAddCompletion(linenoiseCompletions *, const char *);
 
 char *linenoise(const char *prompt);
 int linenoiseHistoryAdd(const char *line);
 int linenoiseHistorySetMaxLen(int len);
-int linenoiseHistorySave(char *filename);
-int linenoiseHistoryLoad(char *filename);
+int linenoiseHistorySave(const char *filename);
+int linenoiseHistoryLoad(const char *filename);
 void linenoiseClearScreen(void);
 void linenoiseSetMultiLine(int ml);