diff --git a/hledger-lib/Hledger/Data/AccountName.hs b/hledger-lib/Hledger/Data/AccountName.hs
index c11fa0c6c..d953ad9b9 100644
--- a/hledger-lib/Hledger/Data/AccountName.hs
+++ b/hledger-lib/Hledger/Data/AccountName.hs
@@ -56,9 +56,11 @@ accountNameLevel a = T.length (T.filter (==acctsepchar) a) + 1
 accountNameDrop :: Int -> AccountName -> AccountName
 accountNameDrop n = accountNameFromComponents . drop n . accountNameComponents
 
--- | ["a:b:c","d:e"] -> ["a","a:b","a:b:c","d","d:e"]
+-- | Sorted unique account names implied by these account names,
+-- ie these plus all their parent accounts up to the root.
+-- Eg: ["a:b:c","d:e"] -> ["a","a:b","a:b:c","d","d:e"]
 expandAccountNames :: [AccountName] -> [AccountName]
-expandAccountNames as = nub $ concatMap expandAccountName as
+expandAccountNames as = nub $ sort $ concatMap expandAccountName as
 
 -- | "a:b:c" -> ["a","a:b","a:b:c"]
 expandAccountName :: AccountName -> [AccountName]
diff --git a/hledger-lib/Hledger/Data/Posting.hs b/hledger-lib/Hledger/Data/Posting.hs
index f6456347f..cee6dee8a 100644
--- a/hledger-lib/Hledger/Data/Posting.hs
+++ b/hledger-lib/Hledger/Data/Posting.hs
@@ -132,8 +132,9 @@ hasAmount = (/= missingmixedamt) . pamount
 isAssignment :: Posting -> Bool
 isAssignment p = not (hasAmount p) && isJust (pbalanceassertion p)
 
+-- | Sorted unique account names referenced by these postings.
 accountNamesFromPostings :: [Posting] -> [AccountName]
-accountNamesFromPostings = nub . map paccount
+accountNamesFromPostings = nub . sort . map paccount
 
 sumPostings :: [Posting] -> MixedAmount
 sumPostings = sumStrict . map pamount