diff --git a/ospf6d/ospf6_main.c b/ospf6d/ospf6_main.c
index b5e6403..95086f2 100644
--- a/ospf6d/ospf6_main.c
+++ b/ospf6d/ospf6_main.c
@@ -92,7 +92,7 @@
 struct thread_master *master;
 
 /* Process ID saved for use by init system */
-char *pid_file = PATH_OSPF6D_PID;
+const char *pid_file = PATH_OSPF6D_PID;
 
 /* Help information display. */
 static void