diff --git a/ospfd/ospf_main.c b/ospfd/ospf_main.c
index 7e1567c..47873ba 100644
--- a/ospfd/ospf_main.c
+++ b/ospfd/ospf_main.c
@@ -97,7 +97,7 @@
 struct thread_master *master;
 
 /* Process ID saved for use by init system */
-char *pid_file = PATH_OSPFD_PID;
+const char *pid_file = PATH_OSPFD_PID;
 
 /* Help information display. */
 static void