diff --git a/css-color-4/Overview.bs b/css-color-4/Overview.bs
index bbd1641495b..0562fcd4838 100644
--- a/css-color-4/Overview.bs
+++ b/css-color-4/Overview.bs
@@ -4298,7 +4298,7 @@ The Predefined CIE XYZ Color Spaces: the ''xyz-d50'', ''xyz-d65'', and ''xyz'' k
 				the reference white for ''xyz-d65''  and ''xyz'' is [=D65=].
 
 				Values greater than 1.0/100% are allowed and must not be clamped;
-				they represent colors brighter than diffuse white.
+				colors where Y is greater than 1.0 represent colors brighter than diffuse white.
 				Values less than 0/0% are uncommon,
 				but can occur as a result of chromatic adaptation,
 				and likewise must not be clamped.