diff --git a/src/log.c b/src/log.c
index f74d4fd..ca42c43 100644
--- a/src/log.c
+++ b/src/log.c
@@ -103,7 +103,7 @@ set_log_level (int level)
  * This routine logs messages to either the log file or the syslog function.
  */
 void
-log_message (int level, char *fmt, ...)
+log_message (int level, const char *fmt, ...)
 {
   va_list args;
   time_t nowtime;
diff --git a/src/log.h b/src/log.h
index 5ee71b8..a31f5e3 100644
--- a/src/log.h
+++ b/src/log.h
@@ -108,7 +108,7 @@ extern int open_log_file (const char *file);
 extern void close_log_file (void);
 extern void truncate_log_file (void);
 
-extern void log_message (int level, char *fmt, ...);
+extern void log_message (int level, const char *fmt, ...);
 extern void set_log_level (int level);
 extern void send_stored_logs (void);