diff --git a/lib/smux.h b/lib/smux.h
index 1d25993..975cf8b 100644
--- a/lib/smux.h
+++ b/lib/smux.h
@@ -146,7 +146,7 @@
 
 void smux_init (struct thread_master *tm, oid [], size_t);
 void smux_start (void);
-void smux_register_mib(char *, struct variable *, size_t, int, oid [], size_t);
+void smux_register_mib(const char *, struct variable *, size_t, int, oid [], size_t);
 int smux_header_generic (struct variable *, oid [], size_t *, int, size_t *, 
     WriteMethod **);
 int smux_trap (oid *, size_t, oid *, size_t, struct trap_object *, size_t, unsigned int, u_char);