diff --git a/isisd/isis_dr.h b/isisd/isis_dr.h
index b0386d4..bad6836 100644
--- a/isisd/isis_dr.h
+++ b/isisd/isis_dr.h
@@ -29,7 +29,7 @@
 int isis_dr_elect (struct isis_circuit *circuit, int level);
 int isis_dr_resign (struct isis_circuit *circuit, int level);
 int isis_dr_commence (struct isis_circuit *circuit, int level);
-char *isis_disflag2string (int disflag);
+const char *isis_disflag2string (int disflag);
 
 enum isis_dis_state
 {