diff --git a/bridge.go b/bridge.go
index 7553ac9..4b2fe92 100644
--- a/bridge.go
+++ b/bridge.go
@@ -37,7 +37,9 @@ func forwardChannel(ctx context.Context, dc *downstreamConn, ch *upstreamChannel
 		}
 	}
 
-	sendNames(dc, ch)
+	if !dc.caps.IsEnabled("soju.im/no-implicit-names") {
+		sendNames(dc, ch)
+	}
 }
 
 func sendTopic(dc *downstreamConn, ch *upstreamChannel) {
diff --git a/doc/ext/no-implicit-names.md b/doc/ext/no-implicit-names.md
new file mode 100644
index 0000000..4c09ffa
--- /dev/null
+++ b/doc/ext/no-implicit-names.md
@@ -0,0 +1,13 @@
+# no-implicit-names
+
+This is a work-in-progress specification.
+
+## Description
+
+This document describes the `no-implicit-names` extension. This allows clients to opt-out from the implicit `NAMES` reply servers send after `JOIN` messages.
+
+Some clients don't need to query the list of channel members for all joined channels. Omitting this information can reduce the time taken to connect to the server, especially on mobile devices and when a large number of channels are joined.
+
+## Implementation
+
+The `no-implicit-names` extension introduces the `soju.im/no-implicit-names` capability. When negotiated, servers MUST NOT send an implicit `NAMES` reply after sending a `JOIN` message. Servers MUST reply to explicit `NAMES` commands sent by the client as usual.
diff --git a/downstream.go b/downstream.go
index c82f7e8..89f6bc5 100644
--- a/downstream.go
+++ b/downstream.go
@@ -231,6 +231,7 @@ var permanentDownstreamCaps = map[string]string{
 
 	"soju.im/bouncer-networks":        "",
 	"soju.im/bouncer-networks-notify": "",
+	"soju.im/no-implicit-names":       "",
 	"soju.im/read":                    "",
 }