diff --git a/src/nu/validator/messages/MessageEmitterAdapter.java b/src/nu/validator/messages/MessageEmitterAdapter.java
index <HASH>..<HASH> 100644
--- a/src/nu/validator/messages/MessageEmitterAdapter.java
+++ b/src/nu/validator/messages/MessageEmitterAdapter.java
@@ -390,6 +390,8 @@ public class MessageEmitterAdapter implements ErrorHandler {
             ".*Unknown pseudo-element or pseudo-class \u201C:focus-within\u201D.*", //
             ".*leader(.+)is not a \u201Ccontent\u201D value.*", //
             ".*Property \u201Cfont-display\u201D doesn't exist.*", //
+            ".*Property \u201Crow-gap\u201D doesn't exist.*", //
+            ".*\u201Cstart\u201D is not a \u201Calign-content\u201D value.*", //
     };
 
     protected static final Pattern DEFAULT_FILTER_PATTERN = Pattern.compile(
Drop CSS row-gap and "align-content: start" errors

This change is a hack to work around the fact the CSS-checking backend
doesn’t yet have support for recognizing the CSS row-gap property
and the "start" value for the align-content property. So rather than
continuing to emit error messages for those (which is wrong, because
they’re not errors...), this change causes the checker to filter out
(drop/ignore/suppress) error messages about those.

Addresses <URL>