diff --git a/hasql-transaction.cabal b/hasql-transaction.cabal
--- a/hasql-transaction.cabal
+++ b/hasql-transaction.cabal
@@ -1,5 +1,5 @@
 name: hasql-transaction
-version: 0.9
+version: 0.9.1
 category: Hasql, Database, PostgreSQL
 synopsis: Composable abstraction over retryable transactions for Hasql
 homepage: https://github.com/nikita-volkov/hasql-transaction
diff --git a/library/Hasql/Transaction.hs b/library/Hasql/Transaction.hs
--- a/library/Hasql/Transaction.hs
+++ b/library/Hasql/Transaction.hs
@@ -11,6 +11,7 @@
   sql,
   session,
   condemn,
+  restrict,
   {-* Settings -}
   Mode(..),
   Level(..),
@@ -139,3 +140,12 @@
 -}
 condemn :: Transaction ()
 condemn = Transaction minBound minBound [put Condemned]
+
+{-|
+Restrict the transaction isolation level.
+
+Will pick up the strictest level among the one you've specified and
+the one associated with the updated transaction.
+-}
+restrict :: Level -> Transaction a -> Transaction a
+restrict newLevel (Transaction mode oldLevel sessions) = Transaction mode (max newLevel oldLevel) sessions