diff --git a/index.bs b/index.bs
index 04c3c0047..ea13051ed 100644
--- a/index.bs
+++ b/index.bs
@@ -2812,7 +2812,8 @@ This method has no arguments and returns a record of capability keys to Boolean
 </xmp>
 
 [=map/Keys=] in {{PublicKeyCredentialClientCapabilities}} MUST be sorted in ascending lexicographical order.
-The set of [=map/keys=] SHOULD equal the set of [=enumeration values=] of {{ClientCapability}}. See also [[#sctn-disclosing-client-capabilities]].
+The set of [=map/keys=] SHOULD equal the set of [=enumeration values=] of {{ClientCapability}},
+but the client MAY omit keys as it deems necessary; see [[#sctn-disclosing-client-capabilities]].
 
 When the value for a given capability is [TRUE], the feature is known to be currently supported by the client.
 When the value for a given capability is [FALSE], the feature is known to be not currently supported by the client.