diff --git a/Database/Persist/Sql/Orphan/PersistQuery.hs b/Database/Persist/Sql/Orphan/PersistQuery.hs
--- a/Database/Persist/Sql/Orphan/PersistQuery.hs
+++ b/Database/Persist/Sql/Orphan/PersistQuery.hs
@@ -214,6 +214,7 @@
     go'' n Subtract = mconcat [n, "=", n, "-?"]
     go'' n Multiply = mconcat [n, "=", n, "*?"]
     go'' n Divide = mconcat [n, "=", n, "/?"]
+    go'' _ (BackendSpecificUpdate up) = error $ T.unpack $ "BackendSpecificUpdate" `mappend` up `mappend` "not supported"
     go' conn (x, pu) = go'' (connEscapeName conn x) pu
     go x = (updateField x, updateUpdate x)
 
diff --git a/Database/Persist/Sql/Orphan/PersistStore.hs b/Database/Persist/Sql/Orphan/PersistStore.hs
--- a/Database/Persist/Sql/Orphan/PersistStore.hs
+++ b/Database/Persist/Sql/Orphan/PersistStore.hs
@@ -51,6 +51,7 @@
             go'' n Subtract = T.concat [n, "=", n, "-?"]
             go'' n Multiply = T.concat [n, "=", n, "*?"]
             go'' n Divide = T.concat [n, "=", n, "/?"]
+            go'' _ (BackendSpecificUpdate up) = error $ T.unpack $ "BackendSpecificUpdate" `mappend` up `mappend` "not supported"
         let go' (x, pu) = go'' (connEscapeName conn x) pu
         let wher = case entityPrimary t of
                 Just pdef -> T.intercalate " AND " $ map (\fld -> connEscapeName conn (fieldDB fld) <> "=? ") $ compositeFields pdef
diff --git a/Database/Persist/Types.hs b/Database/Persist/Types.hs
--- a/Database/Persist/Types.hs
+++ b/Database/Persist/Types.hs
@@ -4,9 +4,10 @@
     ( module Database.Persist.Types.Base
     , SomePersistField (..)
     , Update (..)
+    , BackendSpecificUpdate
     , SelectOpt (..)
-    , BackendSpecificFilter
     , Filter (..)
+    , BackendSpecificFilter
     , Key
     , Entity (..)
     ) where
diff --git a/Database/Persist/Types/Base.hs b/Database/Persist/Types/Base.hs
--- a/Database/Persist/Types/Base.hs
+++ b/Database/Persist/Types/Base.hs
@@ -432,5 +432,6 @@
 instance Exception OnlyUniqueException
 
 
-data PersistUpdate = Assign | Add | Subtract | Multiply | Divide -- FIXME need something else here
-    deriving (Read, Show, Enum, Bounded)
+data PersistUpdate = Assign | Add | Subtract | Multiply | Divide
+                   | BackendSpecificUpdate T.Text
+    deriving (Read, Show)
diff --git a/persistent.cabal b/persistent.cabal
--- a/persistent.cabal
+++ b/persistent.cabal
@@ -1,5 +1,5 @@
 name:            persistent
-version:         2.0.5
+version:         2.0.5.1
 license:         MIT
 license-file:    LICENSE
 author:          Michael Snoyman <michael@snoyman.com>