diff --git a/indexation.cabal b/indexation.cabal
--- a/indexation.cabal
+++ b/indexation.cabal
@@ -1,5 +1,5 @@
 name: indexation
-version: 0.4.2
+version: 0.4.2.1
 category: Data
 synopsis: Tools for entity indexation
 description: A set of tools for indexing entities
@@ -37,10 +37,12 @@
     deferred-folds >=0.6 && <0.7,
     focus >=1.0.1 && <1.1,
     hashable >=1 && <2,
+    list-t >=1 && <1.1,
+    mmorph >=1 && <2,
     potoki >=2 && <2.1,
     potoki-cereal >=0.3 && <0.4,
     profunctors >=5.2 && <6,
-    stm-containers >=1 && <1.1,
+    stm-containers >=1.0.1 && <1.1,
     text >=1 && <2,
     transformers >=0.5 && <0.6,
     unordered-containers >=0.2.9 && <0.3,
diff --git a/library/Indexation/IO.hs b/library/Indexation/IO.hs
--- a/library/Indexation/IO.hs
+++ b/library/Indexation/IO.hs
@@ -39,9 +39,9 @@
 
 freezeIndexerAsVector :: Indexer entity -> IO (Vector entity)
 freezeIndexerAsVector (Indexer sizeVar map) =
-  atomically $ do
-    size <- readTVar sizeVar
-    Vector.unfoldM size (fmap swap (StmMap.unfoldM map))
+  do
+    size <- atomically (readTVar sizeVar)
+    Vector.listTInIO size (hoist atomically (fmap swap (StmMap.listT map)))
 
 freezeIndexerAsEntityTable :: Indexer entity -> IO (EntityTable entity)
 freezeIndexerAsEntityTable = fmap EntityTable . freezeIndexerAsVector
diff --git a/library/Indexation/Prelude.hs b/library/Indexation/Prelude.hs
--- a/library/Indexation/Prelude.hs
+++ b/library/Indexation/Prelude.hs
@@ -118,3 +118,11 @@
 import Potoki.Produce as Exports (Produce)
 import Potoki.Consume as Exports (Consume)
 import Potoki.Transform as Exports (Transform)
+
+-- mmorph
+-------------------------
+import Control.Monad.Morph as Exports hiding (MonadTrans(..))
+
+-- list-t
+-------------------------
+import ListT as Exports (ListT(..))
diff --git a/library/Indexation/Vector.hs b/library/Indexation/Vector.hs
--- a/library/Indexation/Vector.hs
+++ b/library/Indexation/Vector.hs
@@ -6,6 +6,7 @@
 import qualified Data.Vector.Mutable as A
 import qualified Data.HashMap.Strict as B
 import qualified DeferredFolds.UnfoldM as UnfoldM
+import qualified ListT
 
 
 {-|
@@ -51,3 +52,9 @@
       UnfoldM.foldlM' step mv unfoldM
       !iv <- return (unsafeDupablePerformIO (unsafeFreeze mv))
       return iv
+
+listTInIO :: Int -> ListT IO (Int, element) -> IO (Vector element)
+listTInIO size listT = do
+  mv <- A.unsafeNew size
+  flip ListT.traverse_ listT $ \ (index, element) -> A.write mv index element
+  unsafeFreeze mv