diff --git a/Keter/App.hs b/Keter/App.hs
--- a/Keter/App.hs
+++ b/Keter/App.hs
@@ -44,6 +44,7 @@
 import           Keter.Types
 import qualified Network
 import           Prelude                   hiding (FilePath)
+import           System.Environment        (getEnvironment)
 import           System.IO                 (hClose)
 import           System.Posix.Files        (fileAccess)
 import           System.Posix.Types        (EpochTime)
@@ -267,6 +268,7 @@
              -> IO a
 launchWebApp AppStartConfig {..} aid BundleConfig {..} mdir rlog WebAppConfig {..} f = do
     otherEnv <- pluginsGetEnv ascPlugins name bconfigPlugins
+    systemEnv <- getEnvironment
     let httpPort  = kconfigExternalHttpPort  ascKeterConfig
         httpsPort = kconfigExternalHttpsPort ascKeterConfig
         (scheme, extport) =
@@ -277,6 +279,7 @@
             -- Ordering chosen specifically to precedence rules: app specific,
             -- plugins, global, and then auto-set Keter variables.
             [ waconfigEnvironment
+            , Map.filterWithKey (\k _ -> Set.member k waconfigForwardEnv) $ Map.fromList $ map (\x -> (pack (fst x), pack (snd x))) systemEnv
             , Map.fromList otherEnv
             , kconfigEnvironment ascKeterConfig
             , Map.singleton "PORT" $ pack $ show waconfigPort
diff --git a/Keter/Proxy.hs b/Keter/Proxy.hs
--- a/Keter/Proxy.hs
+++ b/Keter/Proxy.hs
@@ -12,7 +12,7 @@
 import qualified Data.ByteString                   as S
 import qualified Data.ByteString.Char8             as S8
 import qualified Data.CaseInsensitive              as CI
-import           Data.Default
+import           Data.Default                      (Default(..))
 import           Data.Monoid                       (mappend, mempty)
 import           Data.Text.Encoding                (encodeUtf8, decodeUtf8With)
 import           Data.Text.Encoding.Error          (lenientDecode)
@@ -35,7 +35,7 @@
                                                     ssListing, staticApp)
 import qualified Network.Wai.Handler.Warp          as Warp
 import qualified Network.Wai.Handler.WarpTLS       as WarpTLS
-import           Network.Wai.Middleware.Gzip       (gzip, def)
+import           Network.Wai.Middleware.Gzip       (gzip)
 import           Prelude                           hiding (FilePath, (++))
 import           WaiAppStatic.Listing              (defaultListing)
 import System.Timeout.Lifted (timeout)
diff --git a/Keter/Types/V04.hs b/Keter/Types/V04.hs
--- a/Keter/Types/V04.hs
+++ b/Keter/Types/V04.hs
@@ -17,7 +17,6 @@
 import Filesystem.Path.CurrentOS (encodeString)
 import Keter.Types.Common
 import Network.HTTP.ReverseProxy.Rewrite
-import qualified Data.Text as T
 
 data AppConfig = AppConfig
     { configExec :: F.FilePath
diff --git a/Keter/Types/V10.hs b/Keter/Types/V10.hs
--- a/Keter/Types/V10.hs
+++ b/Keter/Types/V10.hs
@@ -327,6 +327,7 @@
     , waconfigHosts       :: !(Set Host) -- ^ all hosts, not including the approot host
     , waconfigSsl         :: !Bool
     , waconfigPort        :: !port
+    , waconfigForwardEnv  :: !(Set Text)
     }
     deriving Show
 
@@ -340,6 +341,7 @@
         , waconfigHosts = Set.map CI.mk hosts
         , waconfigSsl = ssl
         , waconfigPort = ()
+        , waconfigForwardEnv = Set.empty
         }
 
 instance ParseYamlFile (WebAppConfig ()) where
@@ -361,6 +363,7 @@
             <*> return hosts
             <*> o .:? "ssl" .!= False
             <*> return ()
+            <*> o .:? "forward-env" .!= Set.empty
 
 instance ToJSON (WebAppConfig ()) where
     toJSON WebAppConfig {..} = object
@@ -369,6 +372,7 @@
         , "env" .= waconfigEnvironment
         , "hosts" .= map CI.original (waconfigApprootHost : Set.toList waconfigHosts)
         , "ssl" .= waconfigSsl
+        , "forward-env" .= waconfigForwardEnv
         ]
 
 data AppInput = AIBundle !FilePath !EpochTime
diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,3 +1,5 @@
+__1.3.6__ Support the `forward-env` setting.
+
 __1.3.5.3__ More correct/complete solution for issue #44. Allows looking up hosts either with or without port numbers.
 
 __1.3.5.2__ Partial workaround for keter.yaml files that give a port with the hostname.
diff --git a/keter.cabal b/keter.cabal
--- a/keter.cabal
+++ b/keter.cabal
@@ -1,5 +1,5 @@
 Name:                keter
-Version:             1.3.5.3
+Version:             1.3.6
 Synopsis:            Web application deployment manager, focusing on Haskell web frameworks
 Description:
     Handles deployment of web apps, providing a reverse proxy to achieve zero downtime deployments. For more information, please see the README on Github: <https://github.com/snoyberg/keter#readme>