diff --git a/tsdb/mapper.go b/tsdb/mapper.go
index 85162728d2..a8a39ffe73 100644
--- a/tsdb/mapper.go
+++ b/tsdb/mapper.go
@@ -49,7 +49,6 @@ type RawMapper struct {
 	whereFields  []string // field names that occur in the where clause
 	selectFields []string // field names that occur in the select clause
 	selectTags   []string // tag keys that occur in the select clause
-	fieldName    string   // the field name being read.
 
 	cursors         []*tagSetCursor // Cursors per tag sets.
 	currCursorIndex int             // Current tagset cursor being drained.