diff --git a/whisper/whisperv6/doc.go b/whisper/whisperv6/doc.go
index 040e1b0dfc..da1b4ee5ba 100644
--- a/whisper/whisperv6/doc.go
+++ b/whisper/whisperv6/doc.go
@@ -58,6 +58,8 @@ const (
 	keyIdSize       = 32 // in bytes
 	bloomFilterSize = 64 // in bytes
 
+	EnvelopeHeaderLength = 20
+
 	MaxMessageSize        = uint32(10 * 1024 * 1024) // maximum accepted size of a message.
 	DefaultMaxMessageSize = uint32(1024 * 1024)
 	DefaultMinimumPoW     = 0.2
diff --git a/whisper/whisperv6/envelope.go b/whisper/whisperv6/envelope.go
index 304608fdeb..9ed712b934 100644
--- a/whisper/whisperv6/envelope.go
+++ b/whisper/whisperv6/envelope.go
@@ -51,7 +51,6 @@ type Envelope struct {
 
 // size returns the size of envelope as it is sent (i.e. public fields only)
 func (e *Envelope) size() int {
-	const EnvelopeHeaderLength = 20
 	return EnvelopeHeaderLength + len(e.Data)
 }