diff --git a/lib/prefix.c b/lib/prefix.c
index 3f3c4e8..8207544 100644
--- a/lib/prefix.c
+++ b/lib/prefix.c
@@ -112,7 +112,7 @@
     }
   else
     {
-      zlog (NULL, LOG_INFO, "prefix_copy(): Unknown address family %d",
+      zlog (NULL, LOG_ERR, "prefix_copy(): Unknown address family %d",
 	      src->family);
       assert (0);
     }