diff --git a/bip-0158.mediawiki b/bip-0158.mediawiki
index 535ffd9a..5ebfaed3 100644
--- a/bip-0158.mediawiki
+++ b/bip-0158.mediawiki
@@ -315,6 +315,8 @@ complete serialization of a filter is:
 * <code>N</code>, encoded as a <code>CompactSize</code>
 * The bytes of the compressed filter itself
 
+A zero element filter MUST be written as one byte containing zeroes.
+
 ==== Signaling ====
 
 This BIP allocates a new service bit: