diff --git a/core/rawdb/ancient_scheme.go b/core/rawdb/ancient_scheme.go
index baf9c78074..b5bf7c6089 100644
--- a/core/rawdb/ancient_scheme.go
+++ b/core/rawdb/ancient_scheme.go
@@ -47,8 +47,8 @@ var chainFreezerTableConfigs = map[string]freezerTableConfig{
 }
 
 type freezerTableConfig struct {
-	snappy   bool
-	prunable bool
+	snappy   bool // enables item compression
+	prunable bool // true for tables that can be truncated by TruncateTailBlocks
 }
 
 const (