diff --git a/client.go b/client.go
index 3eef1580..e18e60f5 100644
--- a/client.go
+++ b/client.go
@@ -89,10 +89,14 @@ const (
 
 	pruneInterval = 10 * time.Second
 
+	// These are our extended message IDs.
 	metadataExtendedId = iota + 1 // 0 is reserved for deleting keys
 	pexExtendedId
 
-	extendedHandshakeClientVersion = "go.torrent dev 20140825"
+	// Updated occasionally to when there's been some changes to client
+	// behaviour in case other clients are assuming anything of us. See also
+	// `bep20`.
+	extendedHandshakeClientVersion = "go.torrent dev 20150624"
 )
 
 // Currently doesn't really queue, but should in the future.
diff --git a/misc.go b/misc.go
index 3cf1b8ee..532d4a72 100644
--- a/misc.go
+++ b/misc.go
@@ -11,10 +11,13 @@ import (
 )
 
 const (
-	pieceHash          = crypto.SHA1
-	maxRequests        = 250        // Maximum pending requests we allow peers to send us.
-	chunkSize          = 0x4000     // 16KiB
-	bep20              = "-GT0000-" // Peer ID client identifier prefix
+	pieceHash   = crypto.SHA1
+	maxRequests = 250    // Maximum pending requests we allow peers to send us.
+	chunkSize   = 0x4000 // 16KiB
+	// Peer ID client identifier prefix. We'll update this occasionally to
+	// reflect changes to client behaviour that other clients may depend on.
+	// Also see `extendedHandshakeClientVersion`.
+	bep20              = "-GT0001-"
 	nominalDialTimeout = time.Second * 30
 	minDialTimeout     = 5 * time.Second
 )