diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+5.21
+ - Picture and Background now provide Eq instances (thanks Jaro Reinders)
+ - #145: vty builds with microlens 0.4.9 (thanks Daniel Wagner)
+ - #142: note requirement of threaded RTS
+
 5.20
 API changes:
  - Split up Monoid instances into Monoid and Semigroup for newer GHCs
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -60,6 +60,11 @@
 * Supports bracketed paste mode as described at
   http://cirw.in/blog/bracketed-paste
 
+# Development Notes
+
+Vty uses threads internally, so programs made with Vty need to be
+compiled with the threaded runtime using the GHC `-threaded` option.
+
 # Platform Support
 
 ## Posix Terminals
diff --git a/src/Graphics/Vty.hs b/src/Graphics/Vty.hs
--- a/src/Graphics/Vty.hs
+++ b/src/Graphics/Vty.hs
@@ -12,6 +12,9 @@
 --   "Graphics.Vty.Image". Output can be syled using 'Attr' (attribute)
 --   values in the "Graphics.Vty.Attributes" module.
 --
+-- Vty uses threads internally, so programs made with Vty need to be
+-- compiled with the threaded runtime using the GHC `-threaded` option.
+--
 -- @
 --  import "Graphics.Vty"
 --
diff --git a/src/Graphics/Vty/Input/Loop.hs b/src/Graphics/Vty/Input/Loop.hs
--- a/src/Graphics/Vty/Input/Loop.hs
+++ b/src/Graphics/Vty/Input/Loop.hs
@@ -24,7 +24,7 @@
 import Control.Concurrent
 import Control.Concurrent.STM
 import Control.Exception (mask, try, SomeException)
-import Lens.Micro
+import Lens.Micro hiding ((<>~))
 import Lens.Micro.Mtl
 import Lens.Micro.TH
 import Control.Monad (when, mzero, forM_)
diff --git a/src/Graphics/Vty/Picture.hs b/src/Graphics/Vty/Picture.hs
--- a/src/Graphics/Vty/Picture.hs
+++ b/src/Graphics/Vty/Picture.hs
@@ -31,7 +31,7 @@
     , picBackground :: Background
     -- ^ The picture's background to be displayed in locations with no
     -- Image data.
-    }
+    } deriving Eq
 
 instance Show Picture where
     show (Picture _ layers _ ) = "Picture ?? " ++ show layers ++ " ??"
@@ -109,6 +109,7 @@
      --
      -- * End of line if there are no remaining non-skip ops.
     | ClearBackground
+    deriving Eq
 
 instance NFData Background where
     rnf (Background c a) = c `seq` a `seq` ()
diff --git a/vty.cabal b/vty.cabal
--- a/vty.cabal
+++ b/vty.cabal
@@ -1,5 +1,5 @@
 name:                vty
-version:             5.20
+version:             5.21
 license:             BSD3
 license-file:        LICENSE
 author:              AUTHORS