diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,12 @@
 
+
+40900.0.0
+=========
+
+ * Endpoints: enabled `mmPatchPost` and removed duplicate argument type
+   for `PostUpdate`.
+ * Ensure that file fetching uses the V4 API endpoint.
+
 40800.0.2
 =========
 
diff --git a/mattermost-api.cabal b/mattermost-api.cabal
--- a/mattermost-api.cabal
+++ b/mattermost-api.cabal
@@ -1,5 +1,5 @@
 name:                mattermost-api
-version:             40800.0.2
+version:             40900.0.0
 synopsis:            Client API for Mattermost chat system
 description:         Client API for Mattermost chat system
 license:             BSD3
diff --git a/src/Network/Mattermost/Endpoints.hs b/src/Network/Mattermost/Endpoints.hs
--- a/src/Network/Mattermost/Endpoints.hs
+++ b/src/Network/Mattermost/Endpoints.hs
@@ -733,15 +733,15 @@
 -- mmUnpinPostToChannel postId =
 --   inPost (printf "/posts/%s/unpin" postId) noBody jsonResponse
 
--- -- | Partially update a post by providing only the fields you want to
--- --   update. Omitted fields will not be updated. The fields that can be
--- --   updated are defined in the request body, all other provided fields
--- --   will be ignored.
--- --
--- --   /Permissions/: Must have the @edit_post@ permission.
--- mmPatchPost :: PostId -> XX27 -> Session -> IO Post
--- mmPatchPost postId body =
---   inPut (printf "/posts/%s/patch" postId) (jsonBody body) jsonResponse
+-- | Partially update a post by providing only the fields you want to
+--   update. Omitted fields will not be updated. The fields that can be
+--   updated are defined in the request body, all other provided fields
+--   will be ignored.
+--
+--   /Permissions/: Must have the @edit_post@ permission.
+mmPatchPost :: PostId -> PostUpdate -> Session -> IO Post
+mmPatchPost postId body =
+  inPut (printf "/posts/%s/patch" postId) (jsonBody body) jsonResponse
 
 data PostQuery = PostQuery
   { postQueryPage    :: Maybe Int
@@ -3483,38 +3483,6 @@
 --   toJSON XX26 { .. } = A.object
 --     [ "message" A..= xx26Message
 --     , "level" A..= xx26Level
---     ]
-
--- --
-
--- data XX27 = XX27
---   { xx27IsPinned :: Bool
---   , xx27Message :: Text
---     -- ^ The message text of the post
---   , xx27HasReactions :: UnknownType
---     -- ^ Set to `true` if the post has reactions to it
---   , xx27FileIds :: (Seq UnknownType)
---     -- ^ The list of files attached to this post
---   , xx27Props :: Text
---     -- ^ A general JSON property bag to attach to the post
---   } deriving (Read, Show, Eq)
-
--- instance A.FromJSON XX27 where
---   parseJSON = A.withObject "xx27" $ \v -> do
---     xx27IsPinned <- v A..: "is_pinned"
---     xx27Message <- v A..: "message"
---     xx27HasReactions <- v A..: "has_reactions"
---     xx27FileIds <- v A..: "file_ids"
---     xx27Props <- v A..: "props"
---     return XX27 { .. }
-
--- instance A.ToJSON XX27 where
---   toJSON XX27 { .. } = A.object
---     [ "is_pinned" A..= xx27IsPinned
---     , "message" A..= xx27Message
---     , "has_reactions" A..= xx27HasReactions
---     , "file_ids" A..= xx27FileIds
---     , "props" A..= xx27Props
 --     ]
 
 -- --
diff --git a/src/Network/Mattermost/Types.hs b/src/Network/Mattermost/Types.hs
--- a/src/Network/Mattermost/Types.hs
+++ b/src/Network/Mattermost/Types.hs
@@ -725,7 +725,7 @@
 
 urlForFile :: FileId -> Text
 urlForFile fId =
-  "/api/v3/files/" <> idString fId <> "/get"
+  "/api/v4/files/" <> idString fId
 
 data PostType
   = PostTypeJoinChannel
@@ -1508,15 +1508,14 @@
     [ "file_ids" A..= p | Just p <- [postUpdateFileIds] ] ++
     [ "props" A..= p | Just p <- [postUpdateProps] ]
 
-postUpdate :: Text -> PostUpdate
-postUpdate message = PostUpdate
-  { postUpdateIsPinned = Nothing
-  , postUpdateMessage = message
-  , postUpdateHasReactions = Nothing
-  , postUpdateFileIds = Nothing
-  , postUpdateProps = Nothing
-  }
-
+postUpdateBody :: Text -> PostUpdate
+postUpdateBody message =
+    PostUpdate { postUpdateIsPinned = Nothing
+               , postUpdateMessage = message
+               , postUpdateHasReactions = Nothing
+               , postUpdateFileIds = Nothing
+               , postUpdateProps = Nothing
+               }
 
 data ChannelPatch = ChannelPatch
   { channelPatchHeader :: Maybe Text