diff --git a/hledger-lib/Hledger/Reports/ReportTypes.hs b/hledger-lib/Hledger/Reports/ReportTypes.hs
index 7f2f09544..8ceb45742 100644
--- a/hledger-lib/Hledger/Reports/ReportTypes.hs
+++ b/hledger-lib/Hledger/Reports/ReportTypes.hs
@@ -156,6 +156,7 @@ data CompoundPeriodicReport a b = CompoundPeriodicReport
   } deriving (Show, Generic, ToJSON)
 
 -- | Description of one subreport within a compound balance report.
+-- Part of a "CompoundBalanceCommandSpec", but also used in hledger-lib.
 data CBCSubreportSpec = CBCSubreportSpec
   { cbcsubreporttitle          :: String
   , cbcsubreportquery          :: Journal -> Query