diff --git a/isisd/isis_main.c b/isisd/isis_main.c
index 64905d3..cd94780 100644
--- a/isisd/isis_main.c
+++ b/isisd/isis_main.c
@@ -96,7 +96,7 @@
 struct thread_master *master;
 
 /* Process ID saved for use by init system */
-char *pid_file = PATH_ISISD_PID;
+const char *pid_file = PATH_ISISD_PID;
 
 /* for reload */
 char _cwd[MAXPATHLEN];