diff --git a/serokell-util.cabal b/serokell-util.cabal
--- a/serokell-util.cabal
+++ b/serokell-util.cabal
@@ -1,5 +1,5 @@
 name:                serokell-util
-version:             0.1.1.1
+version:             0.1.2.0
 synopsis:            General-purpose functions by Serokell
 homepage:            https://github.com/serokell/serokell-util
 license:             MIT
@@ -52,8 +52,8 @@
                        Serokell.Util.Parse.Network
   build-depends:       QuickCheck >= 2.8.1
                      , acid-state
-                     , aeson
-                     , aeson-extra
+                     , aeson >= 0.11.0.0 && <= 1.0.0.0
+                     , aeson-extra >= 0.4.0.0
                      , base >= 4.8 && < 5
                      , base16-bytestring
                      , base64-bytestring
@@ -106,7 +106,7 @@
                        Test.Serokell.Util.TextSpec
                        Spec
   type:                exitcode-stdio-1.0
-  build-depends:       aeson
+  build-depends:       aeson >= 0.11.0.0 && <= 1.0.0.0
                      , base >=4.8
                      , binary
                      , bytestring
diff --git a/src/Serokell/Data/Variant/Serialization.hs b/src/Serokell/Data/Variant/Serialization.hs
--- a/src/Serokell/Data/Variant/Serialization.hs
+++ b/src/Serokell/Data/Variant/Serialization.hs
@@ -104,12 +104,8 @@
 
 --  —————————MessagePack serialization————————— --
 -- MessagePack data structure is very close to Variant. However, note that:
--- 1. We are using strange library where Object type doesn't cover all
---    possible objects. For example, there is only `Int` for integers.
---    So every integer number is converted to `Int` (which may be imprecise).
---    Decoding checks sign of input (like JSON).
--- 2. MessagePack distinguishes between Float and Double while we don't.
--- 3. ObjectExt can't be decoded.
+-- 1. MessagePack distinguishes between Float and Double while we don't.
+-- 2. ObjectExt can't be decoded.
 
 instance MP.MessagePack Variant where
     toObject VarNone = MP.ObjectNil
@@ -126,8 +122,8 @@
         v
     fromObject MP.ObjectNil = pure VarNone
     fromObject (MP.ObjectBool v) = pure . VarBool $ v
-    fromObject (MP.ObjectInt v) | v < 0 = pure . VarInt . fromIntegral $ v
-                                | otherwise = pure . VarUInt . fromIntegral $ v
+    fromObject (MP.ObjectInt v) = pure . VarInt $ v
+    fromObject (MP.ObjectWord v) = pure . VarUInt $ v
     fromObject (MP.ObjectFloat v) = pure . VarFloat . realToFrac $ v
     fromObject (MP.ObjectDouble v) = pure . VarFloat $ v
     fromObject (MP.ObjectStr v) = pure . VarString $ v
diff --git a/src/Serokell/Util/I18N.hs b/src/Serokell/Util/I18N.hs
--- a/src/Serokell/Util/I18N.hs
+++ b/src/Serokell/Util/I18N.hs
@@ -53,7 +53,7 @@
   toReplaceToken = (\(AT.String s) -> s) . genericToJSON defaultOptions
 
 replaceTranslations
-    :: (ToReplaceToken token, Eq lang, Ord lang)
+    :: (ToReplaceToken token, Ord lang)
     => Translations lang token -> lang -> T.Text -> Maybe T.Text
 replaceTranslations translations lang text =
     M.foldrWithKey