diff --git a/siod/editline.c b/siod/editline.c
index 6a1b847..964fe5e 100644
--- a/siod/editline.c
+++ b/siod/editline.c
@@ -176,7 +176,7 @@ STATIC STATUS h_next();
 STATIC STATUS h_prev();
 STATIC STATUS h_first();
 STATIC STATUS h_last();
-STATIC int substrcmp(char *text, char *pat, int len);
+STATIC int substrcmp(const char *text, const char *pat, size_t len);
 STATIC ECHAR *search_hist(ECHAR *search, ECHAR *(*move)());
 STATIC STATUS h_search();
 STATIC STATUS fd_char();
@@ -224,10 +224,10 @@ int		rl_meta_chars = 0;
 */
 STATIC ECHAR	*editinput();
 #if	defined(USE_TERMCAP)
-extern char	*getenv();
-extern char	*tgetstr();
-extern int	tgetent();
-extern int	tgetnum();
+extern char	*getenv(const char *);
+extern char	*tgetstr(char *, char **);
+extern int	tgetent(char *, const char *);
+extern int	tgetnum(char *);
 #endif	/* defined(USE_TERMCAP) */
 
 /*
@@ -806,7 +806,7 @@ STATIC STATUS h_last()
 /*
 **  Return zero if pat appears as a substring in text.
 */
-STATIC int substrcmp(char *text, char *pat, int len)
+STATIC int substrcmp(const char *text, const char *pat, size_t len)
 {
     ECHAR	c;
 
@@ -823,7 +823,7 @@ STATIC ECHAR *search_hist(ECHAR *search, ECHAR *(*move)())
     static ECHAR	*old_search;
     int		len;
     int		pos;
-    int		(*match)();
+    int		(*match)(const char *, const char *, size_t);
     char	*pat;
 
     /* Save or get remembered search pattern. */