diff --git a/zuc/eea.go b/zuc/eea.go
index b5682aa..6c26835 100644
--- a/zuc/eea.go
+++ b/zuc/eea.go
@@ -15,7 +15,6 @@ const (
 	RoundWords = 32
 	// number of bytes in a word
 	WordSize = 4
-	WordMask = WordSize - 1
 	// number of bytes in a round
 	RoundBytes = RoundWords * WordSize
 )