diff --git a/ripd/rip_main.c b/ripd/rip_main.c
index c2128e4..bc25159 100644
--- a/ripd/rip_main.c
+++ b/ripd/rip_main.c
@@ -92,7 +92,7 @@
 struct thread_master *master;
 
 /* Process ID saved for use by init system */
-char *pid_file = PATH_RIPD_PID;
+const char *pid_file = PATH_RIPD_PID;
 
 /* Help information display. */
 static void