diff --git a/frontends/RainTypes.hs b/frontends/RainTypes.hs
index 29c0b4b..b80a22a 100644
--- a/frontends/RainTypes.hs
+++ b/frontends/RainTypes.hs
@@ -96,7 +96,7 @@ performTypeUnification x
              <.< markParamPass
              <.< markAssignmentTypes
              <.< markCommTypes
-             -- TODO mark up types in replicators
+             <.< markReplicators
              <.< markExpressionTypes
              $ x
        -- Then, we do the unification:
@@ -131,6 +131,13 @@ recordInfNameTypes = everywhereM (mkM recordInfNameTypes')
            return input
     recordInfNameTypes' r = return r
 
+markReplicators :: Data t => t -> PassM t
+markReplicators = checkDepthM mark
+  where
+    mark :: Check A.Replicator
+    mark (A.ForEach _m n e)
+      = astTypeOf n >>= \t -> markUnify (A.List t) e
+
 -- | Folds all constants.
 constantFoldPass :: Data t => t -> PassM t
 constantFoldPass = applyDepthM doExpression