diff --git a/.travis.yml b/.travis.yml
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,7 +3,8 @@
 env:
   - GHCVER=7.4.2
   - GHCVER=7.6.3
-  - GHCVER=7.8.3
+  - GHCVER=7.8.4
+  - GHCVER=7.10.1
   - GHCVER=head
   # - >
   #   GHCVER=7.4.2
@@ -37,8 +38,8 @@
 
   # Update happy when building with GHC head
   - |
-    if [ $GHCVER = "head" ] || [ $GHCVER = "7.8.3" ]; then
-      $CABAL install happy alex
+    if [ $GHCVER = "head" ] || [ $GHCVER = "7.8.4" ] || [ $GHCVER = "7.10.1" ]; then
+      $CABAL install --constraint=transformers\ installed happy alex
       export PATH=$HOME/.cabal/bin:$PATH
     fi
 
@@ -51,10 +52,23 @@
   - $CABAL test --show-details=always
   - scripts/stats
 
+  # tests that a source-distribution can be generated
+  - cabal sdist
+
+  # check that the generated source-distribution can be built & installed
+  - export SRC_TGZ=$(cabal info . | awk '{print $2 ".tar.gz";exit}') ;
+    cd dist/;
+    if [ -f "$SRC_TGZ" ]; then
+       cabal install --force-reinstalls "$SRC_TGZ";
+    else
+       echo "expected '$SRC_TGZ' not found";
+       exit 1;
+    fi
+
 notifications:
   irc:
     channels:
       - "irc.freenode.org#haskell-lens"
     skip_join: true
     template:
-      - "\x0313lens\x03/\x0306%{branch}\x03 \x0314%{commit}\x03 %{build_url} %{message}"
+      - "\x0313lens\x0f/\x0306%{branch}\x0f \x0314%{commit}\x0f %{message} \x0302\x1f%{build_url}\x0f"
diff --git a/CHANGELOG.markdown b/CHANGELOG.markdown
--- a/CHANGELOG.markdown
+++ b/CHANGELOG.markdown
@@ -1,3 +1,13 @@
+4.9
+-------
+* `filepath` 1.4 support
+* Removed `Control.Monad.Primitive.Lens` and shed the `primitive` dependency.
+* Add missing `_WithIndex` instances from `keys` package
+* Much more code is inferred `Safe` rather than `Trustworthy`.
+* Documented the difference between `unsafeSingular` and `singular`.
+* `folding` now produces an actual `Fold`.
+* Cleaned up builds for GHC 7.10 to get rid of redundant import warnings.
+
 4.8
 ---
 * When built with `profunctors` 4.4 on GHC 7.8+ we no longer need to use `unsafeCoerce` at all!
@@ -32,7 +42,7 @@
 
 4.6.0.1 [maintenance release]
 -------
-* Compatibility with `base` 4.8
+* Compatibility with `base` 4.8 [Edit: this turned out to not work for the final release of GHC 7.10]
 
 4.6
 ---
diff --git a/lens.cabal b/lens.cabal
--- a/lens.cabal
+++ b/lens.cabal
@@ -1,6 +1,6 @@
 name:          lens
 category:      Data, Lenses, Generics
-version:       4.8
+version:       4.9
 license:       BSD3
 cabal-version: >= 1.8
 license-file:  LICENSE
@@ -189,7 +189,7 @@
     contravariant             >= 0.3      && < 2,
     containers                >= 0.4.0    && < 0.6,
     distributive              >= 0.3      && < 1,
-    filepath                  >= 1.2.0.0  && < 1.4,
+    filepath                  >= 1.2.0.0  && < 1.5,
     free                      >= 4        && < 5,
     ghc-prim,
     hashable                  >= 1.1.2.3  && < 1.3,
@@ -197,7 +197,6 @@
     exceptions                >= 0.1.1    && < 1,
     mtl                       >= 2.0.1    && < 2.3,
     parallel                  >= 3.1.0.1  && < 3.3,
-    primitive                 >= 0.4.0.1  && < 0.6,
     profunctors               >= 4        && < 5,
     reflection                >= 1.1.6    && < 2,
     semigroupoids             >= 4        && < 5,
@@ -263,7 +262,6 @@
     Control.Lens.Wrapped
     Control.Lens.Zoom
     Control.Monad.Error.Lens
-    Control.Monad.Primitive.Lens
     Control.Parallel.Strategies.Lens
     Control.Seq.Lens
     Data.Array.Lens
diff --git a/src/Control/Lens/At.hs b/src/Control/Lens/At.hs
--- a/src/Control/Lens/At.hs
+++ b/src/Control/Lens/At.hs
@@ -40,7 +40,6 @@
   , Contains(..)
   ) where
 
-import Control.Applicative
 import Control.Lens.Each
 import Control.Lens.Traversal
 import Control.Lens.Lens
@@ -68,6 +67,10 @@
 import Data.Vector.Storable as Storable
 import Data.Vector.Unboxed as Unboxed
 import Data.Word
+
+#if !MIN_VERSION_base(4,8,0)
+import Control.Applicative
+#endif
 
 type family Index (s :: *) :: *
 type instance Index (e -> a) = e
diff --git a/src/Control/Lens/Each.hs b/src/Control/Lens/Each.hs
--- a/src/Control/Lens/Each.hs
+++ b/src/Control/Lens/Each.hs
@@ -10,6 +10,10 @@
 #ifdef TRUSTWORTHY
 {-# LANGUAGE Trustworthy #-}
 #endif
+
+#ifndef MIN_VERSION_base
+#define MIN_VERSION_base(x,y,z) 1
+#endif
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Lens.Each
@@ -26,7 +30,6 @@
     Each(..)
   ) where
 
-import Control.Applicative
 import Control.Lens.Iso
 import Control.Lens.Traversal
 import Data.Array.Unboxed as Unboxed
@@ -51,6 +54,10 @@
 import qualified Data.Vector.Unboxed as Unboxed
 import Data.Vector.Unboxed (Unbox)
 import Data.Word
+
+#if !MIN_VERSION_base(4,8,0)
+import Control.Applicative
+#endif
 
 -- $setup
 -- >>> :set -XNoOverloadedStrings
diff --git a/src/Control/Lens/Fold.hs b/src/Control/Lens/Fold.hs
--- a/src/Control/Lens/Fold.hs
+++ b/src/Control/Lens/Fold.hs
@@ -3,9 +3,6 @@
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
-#ifdef TRUSTWORTHY
-{-# LANGUAGE Trustworthy #-}
-#endif
 
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 ----------------------------------------------------------------------------
@@ -194,7 +191,7 @@
 --
 -- >>> [1,2,3,4]^..folding tail
 -- [2,3,4]
-folding :: (Foldable f, Contravariant g, Applicative g) => (s -> f a) -> LensLike g s t a b
+folding :: Foldable f => (s -> f a) -> Fold s a
 folding sfa agb = coerce . traverse_ agb . sfa
 {-# INLINE folding #-}
 
diff --git a/src/Control/Lens/Getter.hs b/src/Control/Lens/Getter.hs
--- a/src/Control/Lens/Getter.hs
+++ b/src/Control/Lens/Getter.hs
@@ -2,9 +2,6 @@
 {-# LANGUAGE Rank2Types #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE FlexibleInstances #-}
-#ifdef TRUSTWORTHY
-{-# LANGUAGE Trustworthy #-}
-#endif
 #if __GLASGOW_HASKELL__ && __GLASGOW_HASKELL__ >= 704
 {-# LANGUAGE NoPolyKinds #-}
 {-# LANGUAGE NoDataKinds #-}
diff --git a/src/Control/Lens/Indexed.hs b/src/Control/Lens/Indexed.hs
--- a/src/Control/Lens/Indexed.hs
+++ b/src/Control/Lens/Indexed.hs
@@ -76,7 +76,11 @@
 
 import Control.Applicative
 import Control.Applicative.Backwards
+import Control.Comonad.Cofree
+import Control.Comonad.Trans.Traced
 import Control.Monad (void, liftM)
+import Control.Monad.Trans.Identity
+import Control.Monad.Trans.Reader
 import Control.Monad.Trans.State.Lazy as Lazy
 import Control.Monad.Free
 import Control.Lens.Fold
@@ -88,17 +92,23 @@
 import Control.Lens.Setter
 import Control.Lens.Traversal
 import Control.Lens.Type
+import Data.Array (Array)
+import qualified Data.Array as Array
 import Data.Foldable
+import Data.Functor.Compose
+import Data.Functor.Product
 import Data.Functor.Reverse
 import Data.Hashable
 import Data.HashMap.Lazy as HashMap
 import Data.IntMap as IntMap
+import Data.Ix (Ix)
 import Data.List.NonEmpty as NonEmpty
 import Data.Map as Map
-import Data.Monoid
+import Data.Monoid hiding (Product)
 import Data.Profunctor.Unsafe
-import Data.Sequence hiding (index)
+import Data.Sequence hiding ((:<), index)
 import Data.Traversable
+import Data.Tree
 import Data.Tuple (swap)
 import Data.Vector (Vector)
 import qualified Data.Vector as V
@@ -744,6 +754,86 @@
 instance TraversableWithIndex i f => TraversableWithIndex [i] (Free f) where
   itraverse f (Pure a) = Pure <$> f [] a
   itraverse f (Free s) = Free <$> itraverse (\i -> itraverse (f . (:) i)) s
+  {-# INLINE itraverse #-}
+
+instance Ix i => FunctorWithIndex i (Array i) where
+  imap f arr = Array.listArray (Array.bounds arr) . fmap (uncurry f) $ Array.assocs arr
+  {-# INLINE imap #-}
+
+instance Ix i => FoldableWithIndex i (Array i) where
+  ifoldMap f = foldMap (uncurry f) . Array.assocs
+  {-# INLINE ifoldMap #-}
+
+instance Ix i => TraversableWithIndex i (Array i) where
+  itraverse f arr = Array.listArray (Array.bounds arr) <$> traverse (uncurry f) (Array.assocs arr)
+  {-# INLINE itraverse #-}
+
+instance FunctorWithIndex i f => FunctorWithIndex [i] (Cofree f) where
+  imap f (a :< as) = f [] a :< imap (\i -> imap (f . (:) i)) as
+  {-# INLINE imap #-}
+
+instance FoldableWithIndex i f => FoldableWithIndex [i] (Cofree f) where
+  ifoldMap f (a :< as) = f [] a `mappend` ifoldMap (\i -> ifoldMap (f . (:) i)) as
+  {-# INLINE ifoldMap #-}
+
+instance TraversableWithIndex i f => TraversableWithIndex [i] (Cofree f) where
+  itraverse f (a :< as) = (:<) <$> f [] a <*> itraverse (\i -> itraverse (f . (:) i)) as
+  {-# INLINE itraverse #-}
+
+instance (FunctorWithIndex i f, FunctorWithIndex j g) => FunctorWithIndex (i, j) (Compose f g) where
+  imap f (Compose fg) = Compose $ imap (\k -> imap (f . (,) k)) fg
+  {-# INLINE imap #-}
+
+instance (FoldableWithIndex i f, FoldableWithIndex j g) => FoldableWithIndex (i, j) (Compose f g) where
+  ifoldMap f (Compose fg) = ifoldMap (\k -> ifoldMap (f . (,) k)) fg
+  {-# INLINE ifoldMap #-}
+
+instance (TraversableWithIndex i f, TraversableWithIndex j g) => TraversableWithIndex (i, j) (Compose f g) where
+  itraverse f (Compose fg) = Compose <$> itraverse (\k -> itraverse (f . (,) k)) fg
+  {-# INLINE itraverse #-}
+
+instance FunctorWithIndex i m => FunctorWithIndex i (IdentityT m) where
+  imap f (IdentityT m) = IdentityT $ imap f m
+  {-# INLINE imap #-}
+
+instance FoldableWithIndex i m => FoldableWithIndex i (IdentityT m) where
+  ifoldMap f (IdentityT m) = ifoldMap f m
+  {-# INLINE ifoldMap #-}
+
+instance TraversableWithIndex i m => TraversableWithIndex i (IdentityT m) where
+  itraverse f (IdentityT m) = IdentityT <$> itraverse f m
+  {-# INLINE itraverse #-}
+
+instance (FunctorWithIndex i f, FunctorWithIndex j g) => FunctorWithIndex (Either i j) (Product f g) where
+  imap f (Pair a b) = Pair (imap (f . Left) a) (imap (f . Right) b)
+  {-# INLINE imap #-}
+
+instance (FoldableWithIndex i f, FoldableWithIndex j g) => FoldableWithIndex (Either i j) (Product f g) where
+  ifoldMap f (Pair a b) = ifoldMap (f . Left) a `mappend` ifoldMap (f . Right) b
+  {-# INLINE ifoldMap #-}
+
+instance (TraversableWithIndex i f, TraversableWithIndex j g) => TraversableWithIndex (Either i j) (Product f g) where
+  itraverse f (Pair a b) = Pair <$> itraverse (f . Left) a <*> itraverse (f . Right) b
+  {-# INLINE itraverse #-}
+
+instance FunctorWithIndex i m => FunctorWithIndex (e, i) (ReaderT e m) where
+  imap f (ReaderT m) = ReaderT $ \k -> imap (f . (,) k) (m k)
+  {-# INLINE imap #-}
+
+instance FunctorWithIndex i w => FunctorWithIndex (s, i) (TracedT s w) where
+  imap f (TracedT w) = TracedT $ imap (\k' g k -> f (k, k') (g k)) w
+  {-# INLINE imap #-}
+
+instance FunctorWithIndex [Int] Tree where
+  imap f (Node a as) = Node (f [] a) $ imap (\i -> imap (f . (:) i)) as
+  {-# INLINE imap #-}
+
+instance FoldableWithIndex [Int] Tree where
+  ifoldMap f (Node a as) = f [] a `mappend` ifoldMap (\i -> ifoldMap (f . (:) i)) as
+  {-# INLINE ifoldMap #-}
+
+instance TraversableWithIndex [Int] Tree where
+  itraverse f (Node a as) = Node <$> f [] a <*> itraverse (\i -> itraverse (f . (:) i)) as
   {-# INLINE itraverse #-}
 
 -------------------------------------------------------------------------------
diff --git a/src/Control/Lens/Internal/Bazaar.hs b/src/Control/Lens/Internal/Bazaar.hs
--- a/src/Control/Lens/Internal/Bazaar.hs
+++ b/src/Control/Lens/Internal/Bazaar.hs
@@ -7,9 +7,6 @@
 #if __GLASGOW_HASKELL__ >= 707
 {-# LANGUAGE RoleAnnotations #-}
 #endif
-#ifdef TRUSTWORTHY
-{-# LANGUAGE Trustworthy #-}
-#endif
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Lens.Internal.Bazaar
diff --git a/src/Control/Lens/Internal/ByteString.hs b/src/Control/Lens/Internal/ByteString.hs
--- a/src/Control/Lens/Internal/ByteString.hs
+++ b/src/Control/Lens/Internal/ByteString.hs
@@ -35,7 +35,10 @@
   , unpackLazy8, traversedLazy8
   ) where
 
+#if !MIN_VERSION_base(4,8,0)
 import Control.Applicative
+#endif
+
 import Control.Lens
 import qualified Data.ByteString               as B
 #if MIN_VERSION_bytestring(0,10,4)
diff --git a/src/Control/Lens/Internal/Context.hs b/src/Control/Lens/Internal/Context.hs
--- a/src/Control/Lens/Internal/Context.hs
+++ b/src/Control/Lens/Internal/Context.hs
@@ -9,9 +9,6 @@
 #if __GLASGOW_HASKELL__ >= 707
 {-# LANGUAGE RoleAnnotations #-}
 #endif
-#ifdef TRUSTWORTHY
-{-# LANGUAGE Trustworthy #-}
-#endif
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Lens.Internal.Context
diff --git a/src/Control/Lens/Internal/Deque.hs b/src/Control/Lens/Internal/Deque.hs
--- a/src/Control/Lens/Internal/Deque.hs
+++ b/src/Control/Lens/Internal/Deque.hs
@@ -3,9 +3,6 @@
 {-# LANGUAGE PatternGuards #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
-#ifdef TRUSTWORTHY
-{-# LANGUAGE Trustworthy #-}
-#endif
 #ifndef MIN_VERSION_base
 #define MIN_VERSION_base(x,y,z) 1
 #endif
diff --git a/src/Control/Lens/Internal/Indexed.hs b/src/Control/Lens/Internal/Indexed.hs
--- a/src/Control/Lens/Internal/Indexed.hs
+++ b/src/Control/Lens/Internal/Indexed.hs
@@ -5,9 +5,6 @@
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
-#ifdef TRUSTWORTHY
-{-# LANGUAGE Trustworthy #-}
-#endif
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Lens.Internal.Indexed
diff --git a/src/Control/Lens/Internal/Magma.hs b/src/Control/Lens/Internal/Magma.hs
--- a/src/Control/Lens/Internal/Magma.hs
+++ b/src/Control/Lens/Internal/Magma.hs
@@ -7,9 +7,6 @@
 {-# LANGUAGE UndecidableInstances #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
-#ifdef TRUSTWORTHY
-{-# LANGUAGE Trustworthy #-}
-#endif
 #if __GLASGOW_HASKELL__ >= 707
 {-# LANGUAGE RoleAnnotations #-}
 #endif
diff --git a/src/Control/Lens/Internal/Prism.hs b/src/Control/Lens/Internal/Prism.hs
--- a/src/Control/Lens/Internal/Prism.hs
+++ b/src/Control/Lens/Internal/Prism.hs
@@ -1,7 +1,4 @@
 {-# LANGUAGE CPP #-}
-#ifdef TRUSTWORTHY
-{-# LANGUAGE Trustworthy #-}
-#endif
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Lens.Internal.Prism
diff --git a/src/Control/Lens/Internal/Reflection.hs b/src/Control/Lens/Internal/Reflection.hs
--- a/src/Control/Lens/Internal/Reflection.hs
+++ b/src/Control/Lens/Internal/Reflection.hs
@@ -10,6 +10,11 @@
 {-# OPTIONS_GHC -fno-full-laziness #-}
 {-# OPTIONS_GHC -fno-float-in #-}
 {-# OPTIONS_GHC -fno-warn-unused-binds #-}
+
+#ifndef MIN_VERSION_base
+#define MIN_VERSION_base(x,y,z) 1
+#endif
+
 ----------------------------------------------------------------------------
 -- |
 -- Module     : Control.Lens.Internal.Reflection
@@ -57,12 +62,15 @@
 import Foreign.Ptr
 import Foreign.StablePtr
 import System.IO.Unsafe
-import Control.Applicative
 import Data.Proxy
 import Data.Bits
 import Data.Word
 import Data.Typeable
 import Data.Reflection
+
+#if !MIN_VERSION_base(4,8,0)
+import Control.Applicative
+#endif
 
 #ifdef HLINT
 {-# ANN module "HLint: ignore Avoid lambda" #-}
diff --git a/src/Control/Lens/Internal/Setter.hs b/src/Control/Lens/Internal/Setter.hs
--- a/src/Control/Lens/Internal/Setter.hs
+++ b/src/Control/Lens/Internal/Setter.hs
@@ -1,7 +1,4 @@
 {-# LANGUAGE CPP #-}
-#ifdef TRUSTWORTHY
-{-# LANGUAGE Trustworthy #-}
-#endif
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Lens.Internal.Setter
diff --git a/src/Control/Lens/Iso.hs b/src/Control/Lens/Iso.hs
--- a/src/Control/Lens/Iso.hs
+++ b/src/Control/Lens/Iso.hs
@@ -2,9 +2,6 @@
 {-# LANGUAGE Rank2Types #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE FunctionalDependencies #-}
-#ifdef TRUSTWORTHY
-{-# LANGUAGE Trustworthy #-}
-#endif
 
 #ifndef MIN_VERSION_bytestring
 #define MIN_VERSION_bytestring(x,y,z) 1
diff --git a/src/Control/Lens/Lens.hs b/src/Control/Lens/Lens.hs
--- a/src/Control/Lens/Lens.hs
+++ b/src/Control/Lens/Lens.hs
@@ -5,9 +5,6 @@
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
-#ifdef TRUSTWORTHY
-{-# LANGUAGE Trustworthy #-}
-#endif
 
 #ifndef MIN_VERSION_mtl
 #define MIN_VERSION_mtl(x,y,z) 1
diff --git a/src/Control/Lens/Level.hs b/src/Control/Lens/Level.hs
--- a/src/Control/Lens/Level.hs
+++ b/src/Control/Lens/Level.hs
@@ -1,9 +1,6 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE Rank2Types #-}
 {-# LANGUAGE FlexibleContexts #-}
-#ifdef TRUSTWORTHY
-{-# LANGUAGE Trustworthy #-}
-#endif
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Lens.Level
diff --git a/src/Control/Lens/Review.hs b/src/Control/Lens/Review.hs
--- a/src/Control/Lens/Review.hs
+++ b/src/Control/Lens/Review.hs
@@ -1,8 +1,5 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE Rank2Types #-}
-#ifdef TRUSTWORTHY
-{-# LANGUAGE Trustworthy #-}
-#endif
 -------------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Lens.Review
diff --git a/src/Control/Lens/Setter.hs b/src/Control/Lens/Setter.hs
--- a/src/Control/Lens/Setter.hs
+++ b/src/Control/Lens/Setter.hs
@@ -3,9 +3,6 @@
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE FlexibleContexts #-}
-#ifdef TRUSTWORTHY
-{-# LANGUAGE Trustworthy #-}
-#endif
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Lens.Setter
diff --git a/src/Control/Lens/TH.hs b/src/Control/Lens/TH.hs
--- a/src/Control/Lens/TH.hs
+++ b/src/Control/Lens/TH.hs
@@ -4,6 +4,10 @@
 {-# LANGUAGE Trustworthy #-}
 #endif
 
+#ifndef MIN_VERSION_base
+#define MIN_VERSION_base(x,y,z) 1
+#endif
+
 #ifndef MIN_VERSION_template_haskell
 #define MIN_VERSION_template_haskell(x,y,z) (defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 706)
 #endif
@@ -54,7 +58,9 @@
   , generateLazyPatterns
   ) where
 
+#if !MIN_VERSION_base(4,8,0)
 import Control.Applicative
+#endif
 #if !(MIN_VERSION_template_haskell(2,7,0))
 import Control.Monad (ap)
 #endif
diff --git a/src/Control/Lens/Traversal.hs b/src/Control/Lens/Traversal.hs
--- a/src/Control/Lens/Traversal.hs
+++ b/src/Control/Lens/Traversal.hs
@@ -7,10 +7,6 @@
 {-# LANGUAGE FunctionalDependencies #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 
-#ifdef TRUSTWORTHY
-{-# LANGUAGE Trustworthy #-}
-#endif
-
 #ifndef MIN_VERSION_containers
 #define MIN_VERSION_containers(x,y,z) 1
 #endif
@@ -630,6 +626,9 @@
 -- >>> [1..10] ^. singular (ix 7)
 -- 8
 --
+-- >>> [] & singular traverse .~ 0
+-- []
+--
 -- @
 -- 'singular' :: 'Traversal' s t a a          -> 'Lens' s t a a
 -- 'singular' :: 'Fold' s a                   -> 'Getter' s a
@@ -654,6 +653,9 @@
 -- The resulting 'Lens' or 'Getter' will be partial if the 'Traversal' targets nothing
 -- or more than one element.
 --
+-- >>> [] & unsafeSingular traverse .~ 0
+-- *** Exception: unsafeSingular: empty traversal
+--
 -- @
 -- 'unsafeSingular' :: 'Traversal' s t a b          -> 'Lens' s t a b
 -- 'unsafeSingular' :: 'Fold' s a                   -> 'Getter' s a
@@ -1222,7 +1224,7 @@
           xs -> unsafeOuts b <$> traverse (corep pafb) xs
           where b = l sell s
 
--- | "Fuse" a 'Traversal' by reassociating all of the '<*>' operations to the
+-- | "Fuse" a 'Traversal' by reassociating all of the '\<*\>' operations to the
 -- left and fusing all of the 'fmap' calls into one. This is particularly
 -- useful when constructing a 'Traversal' using operations from GHC.Generics.
 --
diff --git a/src/Control/Lens/Tuple.hs b/src/Control/Lens/Tuple.hs
--- a/src/Control/Lens/Tuple.hs
+++ b/src/Control/Lens/Tuple.hs
@@ -12,6 +12,10 @@
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE FunctionalDependencies #-}
 
+#ifndef MIN_VERSION_base
+#define MIN_VERSION_base(x,y,z) 1
+#endif
+
 -------------------------------------------------------------------------------
 -- |
 -- Module      :  Control.Lens.Tuple
@@ -38,13 +42,16 @@
   , _1', _2', _3', _4', _5', _6', _7', _8', _9'
   ) where
 
-import Control.Applicative
 import Control.Lens.Lens
 import Data.Functor.Identity
 import Data.Functor.Product
 import Data.Profunctor (dimap)
 import Data.Proxy (Proxy (Proxy))
 import GHC.Generics (Generic (..), (:*:) (..), K1 (..), M1 (..), U1 (..))
+
+#if !MIN_VERSION_base(4,8,0)
+import Control.Applicative
+#endif
 
 -- $setup
 -- >>> :set -XNoOverloadedStrings
diff --git a/src/Control/Lens/Zoom.hs b/src/Control/Lens/Zoom.hs
--- a/src/Control/Lens/Zoom.hs
+++ b/src/Control/Lens/Zoom.hs
@@ -4,9 +4,6 @@
 {-# LANGUAGE UndecidableInstances #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE FunctionalDependencies #-}
-#ifdef TRUSTWORTHY
-{-# LANGUAGE Trustworthy #-}
-#endif
 {-# OPTIONS_GHC -fno-warn-warnings-deprecations #-}
 
 #ifndef MIN_VERSION_mtl
diff --git a/src/Control/Monad/Primitive/Lens.hs b/src/Control/Monad/Primitive/Lens.hs
deleted file mode 100644
--- a/src/Control/Monad/Primitive/Lens.hs
+++ /dev/null
@@ -1,27 +0,0 @@
-{-# LANGUAGE MagicHash #-}
-{-# LANGUAGE UnboxedTuples #-}
-{-# LANGUAGE TypeFamilies #-}
------------------------------------------------------------------------------
--- |
--- Module      :  Control.Monad.Primitive.Lens
--- Copyright   :  (C) 2014-2015 Edward Kmett
--- License     :  BSD-style (see the file LICENSE)
--- Maintainer  :  Edward Kmett <ekmett@gmail.com>
--- Stability   :  provisional
--- Portability :  Control.Monad.Primitive
---
-----------------------------------------------------------------------------
-module Control.Monad.Primitive.Lens
-  (
-    prim
-  ) where
-
-import Control.Lens
-import Control.Monad.Primitive (PrimMonad(..))
-import GHC.Prim (State#)
-
-{-# ANN module "HLint: ignore Unused LANGUAGE pragma" #-}
-
-prim :: (PrimMonad m) => Iso' (m a) (State# (PrimState m) -> (# State# (PrimState m), a #))
-prim = iso internal primitive
-{-# INLINE prim #-}
diff --git a/src/Data/Bits/Lens.hs b/src/Data/Bits/Lens.hs
--- a/src/Data/Bits/Lens.hs
+++ b/src/Data/Bits/Lens.hs
@@ -1,5 +1,11 @@
-{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE Rank2Types #-}
+{-# LANGUAGE FlexibleContexts #-}
+
+#ifndef MIN_VERSION_base
+#define MIN_VERSION_base(x,y,z) 1
+#endif
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.Bits.Lens
@@ -22,8 +28,11 @@
 import Control.Lens
 import Control.Monad.State
 import Data.Bits
-import Data.Functor
 import Data.Word
+
+#if !MIN_VERSION_base(4,8,0)
+import Data.Functor
+#endif
 
 -- $setup
 -- >>> :set -XNoOverloadedStrings
diff --git a/src/Data/Complex/Lens.hs b/src/Data/Complex/Lens.hs
--- a/src/Data/Complex/Lens.hs
+++ b/src/Data/Complex/Lens.hs
@@ -1,5 +1,10 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE FlexibleContexts #-}
+
+#ifndef MIN_VERSION_base
+#define MIN_VERSION_base(x,y,z) 1
+#endif
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.Complex.Lens
@@ -21,9 +26,12 @@
   , _conjugate
   ) where
 
-import Control.Applicative
 import Control.Lens
 import Data.Complex
+
+#if !MIN_VERSION_base(4,8,0)
+import Control.Applicative
+#endif
 
 -- $setup
 -- >>> import Debug.SimpleReflect
diff --git a/src/Data/List/Lens.hs b/src/Data/List/Lens.hs
--- a/src/Data/List/Lens.hs
+++ b/src/Data/List/Lens.hs
@@ -1,5 +1,11 @@
-{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE Rank2Types #-}
+{-# LANGUAGE FlexibleContexts #-}
+
+#ifndef MIN_VERSION_base
+#define MIN_VERSION_base(x,y,z) 1
+#endif
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.List.Lens
@@ -20,8 +26,11 @@
 
 import Control.Monad (guard)
 import Control.Lens
-import Data.Functor
 import Data.List
+
+#if !MIN_VERSION_base(4,8,0)
+import Data.Functor
+#endif
 
 -- $setup
 -- >>> :set -XNoOverloadedStrings
diff --git a/src/Data/Tree/Lens.hs b/src/Data/Tree/Lens.hs
--- a/src/Data/Tree/Lens.hs
+++ b/src/Data/Tree/Lens.hs
@@ -1,4 +1,10 @@
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE FlexibleContexts #-}
+
+#ifndef MIN_VERSION_base
+#define MIN_VERSION_base(x,y,z) 1
+#endif
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.Tree.Lens
@@ -16,8 +22,11 @@
   ) where
 
 import Control.Lens
-import Data.Functor
 import Data.Tree
+
+#if !MIN_VERSION_base(4,8,0)
+import Data.Functor
+#endif
 
 -- | A 'Lens' that focuses on the root of a 'Tree'.
 --
diff --git a/src/Data/Typeable/Lens.hs b/src/Data/Typeable/Lens.hs
--- a/src/Data/Typeable/Lens.hs
+++ b/src/Data/Typeable/Lens.hs
@@ -1,5 +1,10 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE Rank2Types #-}
+
+#ifndef MIN_VERSION_base
+#define MIN_VERSION_base(x,y,z) 1
+#endif
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.Typeable.Lens
@@ -15,10 +20,13 @@
   , _gcast
   ) where
 
-import Control.Applicative
 import Control.Lens
 import Data.Typeable
 import Data.Maybe
+
+#if !MIN_VERSION_base(4,8,0)
+import Control.Applicative
+#endif
 
 -- | A 'Traversal'' for working with a 'cast' of a 'Typeable' value.
 _cast :: (Typeable s, Typeable a) => Traversal' s a
diff --git a/src/Generics/Deriving/Lens.hs b/src/Generics/Deriving/Lens.hs
--- a/src/Generics/Deriving/Lens.hs
+++ b/src/Generics/Deriving/Lens.hs
@@ -3,6 +3,11 @@
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE UndecidableInstances #-}
+
+#ifndef MIN_VERSION_base
+#define MIN_VERSION_base(x,y,z) 1
+#endif
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Generics.Deriving.Lens
@@ -32,12 +37,15 @@
   , GTraversal
   ) where
 
-import           Control.Applicative
 import           Control.Lens
 import           Data.Maybe (fromJust)
 import           Data.Typeable
 import qualified GHC.Generics as Generic
 import           GHC.Generics hiding (from, to)
+
+#if !MIN_VERSION_base(4,8,0)
+import           Control.Applicative
+#endif
 
 -- $setup
 -- >>> :set -XNoOverloadedStrings
diff --git a/src/System/Exit/Lens.hs b/src/System/Exit/Lens.hs
--- a/src/System/Exit/Lens.hs
+++ b/src/System/Exit/Lens.hs
@@ -1,5 +1,11 @@
-{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+
+#ifndef MIN_VERSION_base
+#define MIN_VERSION_base(x,y,z) 1
+#endif
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  System.Exit.Lens
@@ -17,11 +23,14 @@
   , _ExitSuccess
   ) where
 
-import Control.Applicative
 import Control.Exception
 import Control.Exception.Lens
 import Control.Lens
 import System.Exit
+
+#if !MIN_VERSION_base(4,8,0)
+import Control.Applicative
+#endif
 
 -- | Exit codes that a program can return with:
 class AsExitCode p f t where
diff --git a/src/System/FilePath/Lens.hs b/src/System/FilePath/Lens.hs
--- a/src/System/FilePath/Lens.hs
+++ b/src/System/FilePath/Lens.hs
@@ -1,3 +1,9 @@
+{-# LANGUAGE CPP #-}
+
+#ifndef MIN_VERSION_base
+#define MIN_VERSION_base(x,y,z) 1
+#endif
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  System.FilePath.Lens
@@ -17,7 +23,9 @@
   , basename, directory, extension, filename
   ) where
 
+#if !MIN_VERSION_base(4,8,0)
 import Control.Applicative ((<$>))
+#endif
 
 import Control.Monad.State as State
 import System.FilePath