diff --git a/conduit-merge.cabal b/conduit-merge.cabal
--- a/conduit-merge.cabal
+++ b/conduit-merge.cabal
@@ -1,29 +1,25 @@
-name: conduit-merge
-version: 0.1.2.0
-cabal-version: >=1.10
-build-type: Simple
-license: BSD3
-license-file: LICENSE
-copyright: 2016 Yuriy Syrovetskiy
-maintainer: cblp@cblp.su
-homepage: https://github.com/cblp/conduit-merge#readme
-synopsis: Merge multiple sorted conduits
-description:
-    See README.md
-category: Conduit
-author: Yuriy Syrovetskiy
-
-source-repository head
-    type: git
-    location: https://github.com/cblp/conduit-merge
+name:           conduit-merge
+version:        0.1.3.0
+synopsis:       Merge multiple sorted conduits
+description:    See README.md
+homepage:       https://github.com/cblp/conduit-merge#readme
+license:        BSD3
+license-file:   LICENSE
+author:         Yuriy Syrovetskiy
+maintainer:     cblp@cblp.su
+copyright:      2016 Yuriy Syrovetskiy
+category:       Conduit
+build-type:     Simple
+cabal-version:  >= 1.10
 
 library
-    exposed-modules:
-        Data.Conduit.Merge
-    build-depends:
-        base >=4.7 && <5,
-        conduit >=1.2.6.6 && <1.3,
-        mtl >=2.2.1 && <2.3
+    build-depends:    base >= 4.7 && < 5
+                    , conduit >= 1.3 && < 1.4
+                    , mtl
     default-language: Haskell2010
-    hs-source-dirs: src
+    exposed-modules:  Data.Conduit.Merge
+    hs-source-dirs:   src
 
+source-repository head
+    location: https://github.com/cblp/conduit-merge
+    type:     git
diff --git a/src/Data/Conduit/Merge.hs b/src/Data/Conduit/Merge.hs
--- a/src/Data/Conduit/Merge.hs
+++ b/src/Data/Conduit/Merge.hs
@@ -3,27 +3,30 @@
 module Data.Conduit.Merge (mergeSources, mergeSourcesOn) where
 
 import Control.Monad.Trans (lift)
-import Data.Conduit        (Producer, Source, await, newResumableSource, yield, ($$++))
+import Data.Conduit        (ConduitT, await, sealConduitT, yield, ($$++))
 import Data.Foldable       (toList)
 import Data.List           (sortOn)
 
 -- | Merge multiple sorted sources into one sorted producer.
-mergeSources :: (Ord a, Foldable f, Monad m) => f (Source m a) -> Producer m a
+mergeSources :: (Ord a, Foldable f, Monad m) => f (ConduitT () a m ()) -> ConduitT i a m ()
 mergeSources = mergeSourcesOn id
+{-# INLINE mergeSources #-}
 
 -- | Merge multiple sorted sources into one sorted producer using specified sorting key.
-mergeSourcesOn :: (Ord b, Foldable f, Monad m) => (a -> b) -> f (Source m a) -> Producer m a
-mergeSourcesOn key = mergeResumable . fmap newResumableSource . toList
-  where
-    mergeResumable sources = do
+mergeSourcesOn
+    :: (Ord b, Foldable f, Monad m)
+    => (a -> b) -> f (ConduitT () a m ()) -> ConduitT i a m ()
+mergeSourcesOn key = mergeSealed . fmap sealConduitT . toList where
+    mergeSealed sources = do
         prefetchedSources <- lift $ traverse ($$++ await) sources
         go [(a, s) | (s, Just a) <- prefetchedSources]
-    go [] = pure ()
-    go sources = do
-        let (a, src1) : sources1 = sortOn (key . fst) sources
-        yield a
-        (src2, mb) <- lift $ src1 $$++ await
-        let sources2 = case mb of
-                Nothing -> sources1
-                Just b  -> (b, src2) : sources1
-        go sources2
+    go sources =
+        case sortOn (key . fst) sources of
+            []                   -> pure ()
+            (a, src1) : sources1 -> do
+                yield a
+                (src2, mb) <- lift $ src1 $$++ await
+                let sources2 = case mb of
+                        Nothing -> sources1
+                        Just b  -> (b, src2) : sources1
+                go sources2