diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,8 +1,14 @@
 # Changelog
 
+## 0.3
+
+* Breaking: `Applicative` and `Monad` constraint on `m` in
+  `apiToHandler'`. See `rest-core-0.37` for more details.
+
 #### 0.2.10.8
 
 * Allow `rest-core 0.36.*`
+* Allow `rest-gen 0.18.*`
 
 #### 0.2.10.7
 
diff --git a/rest-happstack.cabal b/rest-happstack.cabal
--- a/rest-happstack.cabal
+++ b/rest-happstack.cabal
@@ -1,5 +1,5 @@
 name:                rest-happstack
-version:             0.2.10.8
+version:             0.3
 description:         Rest driver for Happstack.
 synopsis:            Rest driver for Happstack.
 maintainer:          code@silk.co
@@ -28,6 +28,6 @@
     , containers >= 0.4 && < 0.6
     , happstack-server >= 7.0.5 && < 7.5
     , mtl >= 2.0 && < 2.3
-    , rest-core >= 0.34 && < 0.37
-    , rest-gen >= 0.14 && < 0.18
+    , rest-core >= 0.34 && < 0.38
+    , rest-gen >= 0.14 && < 0.20
     , utf8-string >= 0.3 && < 1.1
diff --git a/src/Rest/Driver/Happstack.hs b/src/Rest/Driver/Happstack.hs
--- a/src/Rest/Driver/Happstack.hs
+++ b/src/Rest/Driver/Happstack.hs
@@ -25,7 +25,7 @@
 apiToHandler :: (Functor m, MonadPlus m, MonadIO m) => Api (ServerPartT m) -> ServerPartT m Response
 apiToHandler = apiToHandler' id
 
-apiToHandler' :: (Functor n, MonadPlus n, MonadIO n) => Run m (ServerPartT n) -> Api m -> ServerPartT n Response
+apiToHandler' :: (Applicative m, Functor n, Monad m, MonadPlus n, MonadIO n) => Run m (ServerPartT n) -> Api m -> ServerPartT n Response
 apiToHandler' run api = toResponse <$> Rest.apiToHandler' run api
 
 instance (Functor m, MonadPlus m, MonadIO m) => Rest (ServerPartT m) where