diff --git a/lib/log.c b/lib/log.c
index bbe6e99..375730f 100644
--- a/lib/log.c
+++ b/lib/log.c
@@ -366,7 +366,7 @@
 }
 
 int
-zlog_set_file (struct zlog *zl, int flags, char *filename)
+zlog_set_file (struct zlog *zl, int flags, const char *filename)
 {
   FILE *fp;
   mode_t oldumask;