diff --git a/esqueleto.cabal b/esqueleto.cabal
--- a/esqueleto.cabal
+++ b/esqueleto.cabal
@@ -1,5 +1,5 @@
 name:                esqueleto
-version:             2.0.2
+version:             2.0.3
 synopsis:            Type-safe EDSL for SQL queries on persistent backends.
 homepage:            https://github.com/prowdsponsor/esqueleto
 license:             BSD3
@@ -66,7 +66,7 @@
   build-depends:
       base                 >= 4.5    && < 4.8
     , text                 >= 0.11   && < 1.2
-    , persistent           >= 2.0.5  && < 2.1
+    , persistent           >= 2.0.8  && < 2.1
     , transformers         >= 0.2
     , unordered-containers >= 0.2
     , tagged               >= 0.2
diff --git a/src/Database/Esqueleto.hs b/src/Database/Esqueleto.hs
--- a/src/Database/Esqueleto.hs
+++ b/src/Database/Esqueleto.hs
@@ -375,7 +375,7 @@
 
 -- | @valkey i = val (Key (PersistInt64 i))@
 -- (<https://github.com/meteficha/esqueleto/issues/9>).
-valkey :: (Esqueleto query expr backend, IsSqlKey (Key entity), PersistField (Key entity)) =>
+valkey :: (Esqueleto query expr backend, ToBackendKey SqlBackend entity, PersistField (Key entity)) =>
           Int64 -> expr (Value (Key entity))
 valkey = val . toSqlKey
 
diff --git a/test/Test.hs b/test/Test.hs
--- a/test/Test.hs
+++ b/test/Test.hs
@@ -11,6 +11,7 @@
            , TypeFamilies
            , ScopedTypeVariables
            , CPP
+           , TypeSynonymInstances
  #-}
 module Main (main) where