diff --git a/cblrepo.cabal b/cblrepo.cabal
--- a/cblrepo.cabal
+++ b/cblrepo.cabal
@@ -1,5 +1,5 @@
 name: cblrepo
-version: 0.9.0
+version: 0.9.1
 cabal-version: >= 1.6
 license: OtherLicense
 license-file: LICENSE-2.0
@@ -29,7 +29,8 @@
         directory ==1.2.*, Cabal ==1.16.*, json ==0.7.*,
         bytestring ==0.10.*, tar ==0.4.*, zlib ==0.5.*, mtl >=2.0 && <2.2,
         process ==1.1.*, Unixutils ==1.52.*, unix ==2.6.*,
-        ansi-wl-pprint ==0.6.*, aeson ==0.6.*, optparse-applicative ==0.5.*
+        ansi-wl-pprint ==0.6.*, aeson ==0.6.* && >= 0.6.2,
+        optparse-applicative ==0.5.*
 
 Source-Repository head
     Type:                 git
diff --git a/src/PkgDB.hs b/src/PkgDB.hs
--- a/src/PkgDB.hs
+++ b/src/PkgDB.hs
@@ -29,7 +29,7 @@
 import qualified Distribution.Version as V
 
 import Data.Aeson (decode, encode)
-import Data.Aeson.TH (deriveJSON)
+import Data.Aeson.TH (deriveJSON, defaultOptions, Options(..), SumEncoding(..))
 import qualified Data.ByteString.Lazy.Char8 as C
 
 -- {{{ temporary
@@ -188,11 +188,10 @@
         s = C.unlines $ map encode $ sort db
 
 -- {{{1 JSON instances
--- $(deriveJSON id ''CblPkg)
-$(deriveJSON id ''V.Version)
-$(deriveJSON id ''V.VersionRange)
-$(deriveJSON id ''P.Dependency)
-$(deriveJSON id ''P.PackageName)
-$(deriveJSON id ''FlagName)
-$(deriveJSON id ''Pkg)
-$(deriveJSON id ''CblPkg)
+$(deriveJSON defaultOptions { sumEncoding = ObjectWithSingleField, allNullaryToStringTag = False } ''V.Version)
+$(deriveJSON defaultOptions { sumEncoding = ObjectWithSingleField, allNullaryToStringTag = False } ''V.VersionRange)
+$(deriveJSON defaultOptions { sumEncoding = ObjectWithSingleField, allNullaryToStringTag = False } ''P.Dependency)
+$(deriveJSON defaultOptions { sumEncoding = ObjectWithSingleField, allNullaryToStringTag = False } ''P.PackageName)
+$(deriveJSON defaultOptions { sumEncoding = ObjectWithSingleField, allNullaryToStringTag = False } ''FlagName)
+$(deriveJSON defaultOptions { sumEncoding = ObjectWithSingleField, allNullaryToStringTag = False } ''Pkg)
+$(deriveJSON defaultOptions { sumEncoding = ObjectWithSingleField, allNullaryToStringTag = False } ''CblPkg)