diff --git a/.travis.yml b/.travis.yml
index 7399e47..b44040b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,7 +5,8 @@ node_js: stable
 env:
   - PATH=$HOME/purescript:$PATH
 install:
-  - TAG=$(basename $(curl --location --silent --output /dev/null -w %{url_effective} https://github.com/purescript/purescript/releases/latest))
+  # - TAG=$(basename $(curl --location --silent --output /dev/null -w %{url_effective} https://github.com/purescript/purescript/releases/latest))
+  - TAG=v0.14.0-rc2
   - curl --location --output $HOME/purescript.tar.gz https://github.com/purescript/purescript/releases/download/$TAG/linux64.tar.gz
   - tar -xvf $HOME/purescript.tar.gz -C $HOME/
   - chmod a+x $HOME/purescript
diff --git a/bower.json b/bower.json
index a6ed0e8..3180c1f 100644
--- a/bower.json
+++ b/bower.json
@@ -17,6 +17,7 @@
     "package.json"
   ],
   "dependencies": {
-    "purescript-prelude": "^4.0.0"
+    "purescript-prelude": "master",
+    "purescript-safe-coerce": "master"
   }
 }
diff --git a/package.json b/package.json
index d34ea78..b8d0c47 100644
--- a/package.json
+++ b/package.json
@@ -6,7 +6,7 @@
   },
   "devDependencies": {
     "pulp": "^15.0.0",
-    "purescript-psa": "^0.6.0",
+    "purescript-psa": "^0.8.0",
     "rimraf": "^2.6.2"
   }
 }
diff --git a/src/Data/Newtype.purs b/src/Data/Newtype.purs
index 5f7c15d..b1d6db5 100644
--- a/src/Data/Newtype.purs
+++ b/src/Data/Newtype.purs
@@ -2,7 +2,6 @@ module Data.Newtype where
 
 import Prelude
 
-import Data.Function (on)
 import Data.Monoid.Additive (Additive(..))
 import Data.Monoid.Conj (Conj(..))
 import Data.Monoid.Disj (Disj(..))
@@ -11,6 +10,8 @@ import Data.Monoid.Endo (Endo(..))
 import Data.Monoid.Multiplicative (Multiplicative(..))
 import Data.Semigroup.First (First(..))
 import Data.Semigroup.Last (Last(..))
+import Prim.Coerce (class Coercible)
+import Safe.Coerce (coerce)
 
 -- | A type class for `newtype`s to enable convenient wrapping and unwrapping,
 -- | and the use of the other functions in this module.
@@ -33,6 +34,7 @@ import Data.Semigroup.Last (Last(..))
 -- | unwrap <<< wrap = id
 -- | wrap <<< unwrap = id
 -- | ```
+class Newtype :: Type -> Type -> Constraint
 class Newtype t a | t -> a where
   wrap :: a -> t
   unwrap :: t -> a
@@ -74,10 +76,6 @@ instance newtypeLast :: Newtype (Last a) a where
 un :: forall t a. Newtype t a => (a -> t) -> t -> a
 un _ = unwrap
 
--- | Deprecated previous name of `un`.
-op :: forall t a. Newtype t a => (a -> t) -> t -> a
-op = un
-
 -- | This combinator is for when you have a higher order function that you want
 -- | to use in the context of some newtype - `foldMap` being a common example:
 -- |
@@ -90,12 +88,13 @@ op = un
 ala
   :: forall f t a s b
    . Functor f
+  => Coercible (f t) (f a)
   => Newtype t a
   => Newtype s b
   => (a -> t)
   -> ((b -> s) -> f t)
   -> f a
-ala _ f = map unwrap (f wrap)
+ala _ f = coerce (f wrap)
 
 -- | Similar to `ala` but useful for cases where you want to use an additional
 -- | projection with the higher order function:
@@ -111,14 +110,16 @@ ala _ f = map unwrap (f wrap)
 alaF
   :: forall f g t a s b
    . Functor f
+  => Coercible (f t) (f a)
   => Functor g
+  => Coercible (g s) (g b)
   => Newtype t a
   => Newtype s b
   => (a -> t)
   -> (f t -> g s)
   -> f a
   -> g b
-alaF _ f = map unwrap <<< f <<< map wrap
+alaF _ = coerce
 
 -- | Lifts a function operate over newtypes. This can be used to lift a
 -- | function to manipulate the contents of a single newtype, somewhat like
@@ -144,13 +145,15 @@ alaF _ f = map unwrap <<< f <<< map wrap
 -- | ```
 over
   :: forall t a s b
-   . Newtype t a
+   . Coercible a t
+  => Coercible b s
+  => Newtype t a
   => Newtype s b
   => (a -> t)
   -> (a -> b)
   -> t
   -> s
-over _ f = wrap <<< f <<< unwrap
+over _ = coerce
 
 -- | Much like `over`, but where the lifted function operates on values in a
 -- | `Functor`:
@@ -165,14 +168,16 @@ over _ f = wrap <<< f <<< unwrap
 overF
   :: forall f g t a s b
    . Functor f
+  => Coercible (f a) (f t)
   => Functor g
+  => Coercible (g b) (g s)
   => Newtype t a
   => Newtype s b
   => (a -> t)
   -> (f a -> g b)
   -> f t
   -> g s
-overF _ f = map wrap <<< f <<< map unwrap
+overF _ = coerce
 
 -- | The opposite of `over`: lowers a function that operates on `Newtype`d
 -- | values to operate on the wrapped value instead.
@@ -197,13 +202,15 @@ overF _ f = map wrap <<< f <<< map unwrap
 -- | a `Number` in and get a `Number` out via `under`.
 under
   :: forall t a s b
-   . Newtype t a
+   . Coercible t a
+  => Coercible s b
+  => Newtype t a
   => Newtype s b
   => (a -> t)
   -> (t -> s)
   -> a
   -> b
-under _ f = unwrap <<< f <<< wrap
+under _ = coerce
 
 -- | Much like `under`, but where the lifted function operates on values in a
 -- | `Functor`:
@@ -224,14 +231,16 @@ under _ f = unwrap <<< f <<< wrap
 underF
   :: forall f g t a s b
    . Functor f
+  => Coercible (f t) (f a)
   => Functor g
+  => Coercible (g s) (g b)
   => Newtype t a
   => Newtype s b
   => (a -> t)
   -> (f t -> g s)
   -> f a
   -> g b
-underF _ f = map unwrap <<< f <<< map wrap
+underF _ = coerce
 
 -- | Lifts a binary function to operate over newtypes.
 -- |
@@ -249,21 +258,25 @@ underF _ f = map unwrap <<< f <<< map wrap
 -- | here too.
 over2
   :: forall t a s b
-   . Newtype t a
+   . Coercible a t
+  => Coercible b s
+  => Newtype t a
   => Newtype s b
   => (a -> t)
   -> (a -> a -> b)
   -> t
   -> t
   -> s
-over2 _ f = compose wrap <<< f `on` unwrap
+over2 _ = coerce
 
 -- | Much like `over2`, but where the lifted binary function operates on
 -- | values in a `Functor`.
 overF2
   :: forall f g t a s b
    . Functor f
+  => Coercible (f a) (f t)
   => Functor g
+  => Coercible (g b) (g s)
   => Newtype t a
   => Newtype s b
   => (a -> t)
@@ -271,27 +284,31 @@ overF2
   -> f t
   -> f t
   -> g s
-overF2 _ f = compose (map wrap) <<< f `on` map unwrap
+overF2 _ = coerce
 
 -- | The opposite of `over2`: lowers a binary function that operates on `Newtype`d
 -- | values to operate on the wrapped value instead.
 under2
   :: forall t a s b
-   . Newtype t a
+   . Coercible t a
+  => Coercible s b
+  => Newtype t a
   => Newtype s b
   => (a -> t)
   -> (t -> t -> s)
   -> a
   -> a
   -> b
-under2 _ f = compose unwrap <<< f `on` wrap
+under2 _ = coerce
 
 -- | Much like `under2`, but where the lifted binary function operates on
 -- | values in a `Functor`.
 underF2
   :: forall f g t a s b
    . Functor f
+  => Coercible (f t) (f a)
   => Functor g
+  => Coercible (g s) (g b)
   => Newtype t a
   => Newtype s b
   => (a -> t)
@@ -299,28 +316,33 @@ underF2
   -> f a
   -> f a
   -> g b
-underF2 _ f = compose (map unwrap) <<< f `on` map wrap
+underF2 _ = coerce
 
 -- | Similar to the function from the `Traversable` class, but operating within
 -- | a newtype instead.
 traverse
   :: forall f t a
    . Functor f
+  => Coercible (f a) (f t)
+  => Coercible t a
+  => Coercible a t
   => Newtype t a
   => (a -> t)
   -> (a -> f a)
   -> t
   -> f t
-traverse _ f = map wrap <<< f <<< unwrap
+traverse _ = coerce
 
 -- | Similar to the function from the `Distributive` class, but operating within
 -- | a newtype instead.
 collect
   :: forall f t a
    . Functor f
+  => Coercible a t
+  => Coercible (f a) (f t)
   => Newtype t a
   => (a -> t)
   -> (f a -> a)
   -> f t
   -> t
-collect _ f = wrap <<< f <<< map unwrap
+collect _ = coerce