diff --git a/lib/log.h b/lib/log.h
index 8609791..2dd1d31 100644
--- a/lib/log.h
+++ b/lib/log.h
@@ -151,7 +151,7 @@
 #define LOOKUP(x, y) mes_lookup(x, x ## _max, y, "(no item found)")
 
 extern const char *lookup (const struct message *, int);
-extern const char *mes_lookup (struct message *meslist, 
+extern const char *mes_lookup (const struct message *meslist, 
                                int max, int index,
                                const char *no_item);