diff --git a/hledger-lib/Hledger/Data/Valuation.hs b/hledger-lib/Hledger/Data/Valuation.hs
index 327ed6458c4..5c1349cdfb6 100644
--- a/hledger-lib/Hledger/Data/Valuation.hs
+++ b/hledger-lib/Hledger/Data/Valuation.hs
@@ -27,7 +27,7 @@ import Data.Decimal (roundTo)
 import Data.Function (on)
 import Data.Graph.Inductive  (Gr, Node, NodeMap, mkMapGraph, mkNode, lab, out, sp)
 import Data.List
--- import Data.List.Extra (nubSortBy)
+import Data.List.Extra (nubSortBy)
 import qualified Data.Map as M
 import Data.Maybe
 import qualified Data.Text as T
@@ -120,9 +120,7 @@ pricesAtDate pricedirectives d = PriceGraph{prGraph=g, prNodemap=m, prDeclaredPa
     -- get the latest (on or before date d) declared price for each commodity pair
     declaredprices :: [MarketPrice] =
       dbg5 "declaredprices" $
-      -- XXX Data.List.Extra.nubSortBy might be more efficient (n Log n vs n^2 ?)
-      -- but is not in ghc 7.10, 8.0 stackage snapshots
-      nub $ sortBy (compare `on` (\(MarketPrice{..})->(mpfrom,mpto))) $  -- keep only the first (ie newest and latest parsed) price for each pair
+      nubSortBy (compare `on` (\(MarketPrice{..})->(mpfrom,mpto))) $  -- keep only the first (ie newest and latest parsed) price for each pair
       map snd $  -- discard the parse order label
       sortBy (flip compare `on` (\(parseorder,mp)->(mpdate mp,parseorder))) $  -- sort with newest dates and latest parse order first
       zip [1..] $  -- label with parse order
diff --git a/hledger-lib/hledger-lib.cabal b/hledger-lib/hledger-lib.cabal
index 9f5d192a5b9..1b44884dbb1 100644
--- a/hledger-lib/hledger-lib.cabal
+++ b/hledger-lib/hledger-lib.cabal
@@ -4,7 +4,7 @@ cabal-version: 1.12
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 940be6dde18cf33cca2096d9176100b9ba178418eea2f1427d94fc5ffe58e783
+-- hash: 4cfc4e9879ec711800e91c2cfe108a99c36d80ccb81b59e1df314915e94d5523
 
 name:           hledger-lib
 version:        1.14.99
@@ -120,7 +120,7 @@ library
     , deepseq
     , directory
     , easytest >=0.2.1 && <0.3
-    , extra
+    , extra >=1.6.3
     , fgl >=5.5.4.0
     , file-embed >=0.0.10
     , filepath
@@ -223,7 +223,7 @@ test-suite doctests
     , directory
     , doctest >=0.16
     , easytest >=0.2.1 && <0.3
-    , extra
+    , extra >=1.6.3
     , fgl >=5.5.4.0
     , file-embed >=0.0.10
     , filepath
@@ -325,7 +325,7 @@ test-suite easytests
     , deepseq
     , directory
     , easytest >=0.2.1 && <0.3
-    , extra
+    , extra >=1.6.3
     , fgl >=5.5.4.0
     , file-embed >=0.0.10
     , filepath
diff --git a/hledger-lib/package.yaml b/hledger-lib/package.yaml
index 91a94e56042..944b8f37155 100644
--- a/hledger-lib/package.yaml
+++ b/hledger-lib/package.yaml
@@ -76,7 +76,7 @@ dependencies:
 - transformers >=0.2
 - uglymemo
 - utf8-string >=0.3.5
-- extra
+- extra >=1.6.3
 - Glob >= 0.9
 # for ledger-parse:
 #- parsers >=0.5
diff --git a/stack-ghc7.10.yaml b/stack-ghc7.10.yaml
index 06d17886ba3..a4009994fe4 100644
--- a/stack-ghc7.10.yaml
+++ b/stack-ghc7.10.yaml
@@ -35,6 +35,7 @@ extra-deps:
 - directory-1.2.7.0
 - doctest-0.16.0
 - exceptions-0.10.0
+- extra-1.6.17
 - fgl-5.5.4.0
 - free-5.0.2
 - generics-sop-0.3.2.0
diff --git a/stack-ghc8.0.yaml b/stack-ghc8.0.yaml
index 2a8e3d048de..0a0b248f47a 100644
--- a/stack-ghc8.0.yaml
+++ b/stack-ghc8.0.yaml
@@ -24,6 +24,7 @@ extra-deps:
 - config-ini-0.2.3.0
 - criterion-1.4.1.0
 - doctest-0.16.0
+- extra-1.6.17
 - fgl-5.5.4.0
 - generics-sop-0.3.2.0
 - hashable-1.2.7.0