diff --git a/bgpwtf/machines/tests/edge01-waw.nix b/bgpwtf/machines/tests/edge01-waw.nix
index 1d724e1..6b641b5 100644
--- a/bgpwtf/machines/tests/edge01-waw.nix
+++ b/bgpwtf/machines/tests/edge01-waw.nix
@@ -262,7 +262,7 @@
     # edge01 must announce exactly one v4 prefix.
     bgpspeaker.succeed("birdc show route protocol bgp_globalmix_v4 | grep unicast")
     bgpspeaker.fail(
-        "birdc show route protocol bgp_globalmix_v4 | grep unicast | grep -v 185.236.240.0/23"
+        "birdc show route protocol bgp_globalmix_v4 | grep unicast | grep -v 185.236.240.0/24"
     )
 
     # edge01 must announce exactly one v6 prefix.