diff --git a/esqueleto.cabal b/esqueleto.cabal
index debe59f..5223c7d 100644
--- a/esqueleto.cabal
+++ b/esqueleto.cabal
@@ -66,7 +66,7 @@ library
       base                 >= 4.8     && < 5.0
     , bytestring
     , text                 >= 0.11    && < 1.3
-    , persistent           >= 2.5     && < 2.8
+    , persistent           >= 2.7.1   && < 2.8
     , transformers         >= 0.2
     , unordered-containers >= 0.2
     , tagged               >= 0.2
diff --git a/src/Database/Esqueleto/Internal/Language.hs b/src/Database/Esqueleto/Internal/Language.hs
index 291d102..6ba0075 100644
--- a/src/Database/Esqueleto/Internal/Language.hs
+++ b/src/Database/Esqueleto/Internal/Language.hs
@@ -54,19 +54,6 @@ import qualified Data.ByteString as B
 import qualified Data.Text as T
 import qualified Data.Text.Lazy as TL
 
-class BackendCompatible sup sub where
-  projectBackend :: sub -> sup
-
-instance BackendCompatible SqlBackend SqlBackend where
-  projectBackend = id
-
-instance BackendCompatible SqlBackend SqlReadBackend where
-  projectBackend = unSqlReadBackend
-
-instance BackendCompatible SqlBackend SqlWriteBackend where
-  projectBackend = unSqlWriteBackend
-
-
 -- | Finally tagless representation of @esqueleto@'s EDSL.
 class (Functor query, Applicative query, Monad query) =>
       Esqueleto query expr backend | query -> expr backend, expr -> query backend where
diff --git a/stack-7.10.yaml b/stack-7.10.yaml
index f3e0bd7..318facf 100644
--- a/stack-7.10.yaml
+++ b/stack-7.10.yaml
@@ -3,4 +3,4 @@ packages:
 - '.'
 resolver: lts-6.12
 extra-deps:
-  - persistent-2.5
+  - persistent-2.7.1
diff --git a/stack-8.0.yaml b/stack-8.0.yaml
index 5b854e7..1d884b7 100644
--- a/stack-8.0.yaml
+++ b/stack-8.0.yaml
@@ -7,6 +7,7 @@ packages:
 extra-deps:
 - doctest-prop-0.2.0.1
 - quickcheck-properties-0.1
+- persistent-2.7.1
 # - http-client-0.5.0
 # - fail-4.9.0.0
 # - http-types-0.9