diff --git a/activitystreams/tag.go b/activitystreams/tag.go
index 63fe4c4..38010bf 100644
--- a/activitystreams/tag.go
+++ b/activitystreams/tag.go
@@ -10,5 +10,5 @@ type TagType string
 
 const (
 	TagHashtag TagType = "Hashtag"
-	TagMention         = "Mention"
+	TagMention TagType = "Mention"
 )