diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,15 @@
 [The latest version of this document is on GitHub.](https://github.com/haskell-servant/servant/blob/master/servant/CHANGELOG.md)
 
+0.16.1
+------
+
+* Add `Semigroup` and `Monoid` `SourceT` instances
+  [#1158](https://github.com/haskell-servant/servant/pull/1158)
+  [#1159](https://github.com/haskell-servant/servant/pull/1159)
+* Use `http-api-data-0.4.1`
+  [#1181](https://github.com/haskell-servant/servant/pull/1181)
+* Allow newer dependencies
+
 0.16.0.1
 --------
 
diff --git a/servant.cabal b/servant.cabal
--- a/servant.cabal
+++ b/servant.cabal
@@ -1,6 +1,6 @@
 cabal-version:       >=1.10
 name:                servant
-version:             0.16.0.1
+version:             0.16.1
 
 synopsis:            A family of combinators for defining webservices APIs
 category:            Servant, Web
@@ -24,7 +24,8 @@
   GHC ==8.0.2
    || ==8.2.2
    || ==8.4.4
-   || ==8.6.4
+   || ==8.6.5
+   || ==8.8.1
 
 extra-source-files:
   CHANGELOG.md
@@ -98,7 +99,7 @@
   -- We depend (heavily) on the API of these packages:
   -- i.e. re-export, or allow using without direct dependency
   build-depends:
-      http-api-data          >= 0.4      && < 0.4.1
+      http-api-data          >= 0.4.1    && < 0.4.2
     , singleton-bool         >= 0.1.4    && < 0.1.5
 
   -- Other dependencies: Lower bound around what is in the latest Stackage LTS.
diff --git a/src/Servant/Types/SourceT.hs b/src/Servant/Types/SourceT.hs
--- a/src/Servant/Types/SourceT.hs
+++ b/src/Servant/Types/SourceT.hs
@@ -89,6 +89,21 @@
     hoist f (SourceT m) = SourceT $ \k -> k $
         Effect $ f $ fmap (hoist f) $ m return
 
+-- | >>> source "xy" <> source "z" :: SourceT Identity Char
+-- fromStepT (Effect (Identity (Yield 'x' (Yield 'y' (Yield 'z' Stop)))))
+--
+instance Functor m => Semigroup (SourceT m a) where
+    SourceT withL <> SourceT withR = SourceT $ \ret ->
+        withL $ \l ->
+        withR $ \r ->
+        ret $ l <> r
+
+-- | >>> mempty :: SourceT Maybe Int
+-- fromStepT (Effect (Just Stop))
+instance Functor m => Monoid (SourceT m a) where
+    mempty = fromStepT mempty
+    mappend = (<>)
+
 -- | Doesn't generate 'Error' constructors. 'SourceT' doesn't shrink.
 instance (QC.Arbitrary a, Monad m) => QC.Arbitrary (SourceT m a) where
     arbitrary = fromStepT <$> QC.arbitrary
@@ -149,6 +164,23 @@
         go (Skip s)    = Skip (go s)
         go (Yield x s) = Yield x (go s)
         go (Effect ms) = Effect (f (fmap go ms))
+
+instance Functor m => Semigroup (StepT m a) where
+    Stop      <> r = r
+    Error err <> _ = Error err
+    Skip s    <> r = Skip (s <> r)
+    Yield x s <> r = Yield x (s <> r)
+    Effect ms <> r = Effect ((<> r) <$> ms)
+
+-- | >>> mempty :: StepT [] Int
+-- Stop
+--
+-- >>> mempty :: StepT Identity Int
+-- Stop
+--
+instance Functor m => Monoid (StepT m a) where
+    mempty = Stop
+    mappend = (<>)
 
 -- | Doesn't generate 'Error' constructors.
 instance (QC.Arbitrary a, Monad m) => QC.Arbitrary (StepT m a) where