diff --git a/protolude.cabal b/protolude.cabal
--- a/protolude.cabal
+++ b/protolude.cabal
@@ -1,5 +1,5 @@
 name:                protolude
-version:             0.1.4
+version:             0.1.5
 synopsis:            A sensible set of defaults for writing custom Preludes.
 description:         A sensible set of defaults for writing custom Preludes.
 homepage:            https://github.com/sdiehl/protolude
@@ -45,6 +45,7 @@
     Show
     Either
     Functor
+    Semiring
     Bifunctor
 
   default-extensions:
@@ -64,7 +65,6 @@
     async            >= 2.1  && <2.2,
     deepseq          >= 1.3  && <= 1.5,
     containers       >= 0.5  && <0.6,
-    semiring-simple  >= 0.1  && <1.1,
     mtl              >= 2.1  && <2.3,
     transformers     >= 0.4  && < 0.6,
     text             >= 1.2  && <1.3,
diff --git a/src/Base.hs b/src/Base.hs
--- a/src/Base.hs
+++ b/src/Base.hs
@@ -17,6 +17,10 @@
 import GHC.Enum as X
 import GHC.Real as X
 import GHC.Float as X
+import GHC.Err as X (
+    undefined
+  , error
+  )
 import GHC.Show as X (
     Show(..)
   )
diff --git a/src/Bifunctor.hs b/src/Bifunctor.hs
--- a/src/Bifunctor.hs
+++ b/src/Bifunctor.hs
@@ -10,38 +10,38 @@
 import Control.Applicative ( Const(..) )
 
 class Bifunctor p where
-    {-# MINIMAL bimap | first, second #-}
+  {-# MINIMAL bimap | first, second #-}
 
-    bimap :: (a -> b) -> (c -> d) -> p a c -> p b d
-    bimap f g = first f . second g
+  bimap :: (a -> b) -> (c -> d) -> p a c -> p b d
+  bimap f g = first f . second g
 
-    first :: (a -> b) -> p a c -> p b c
-    first f = bimap f id
+  first :: (a -> b) -> p a c -> p b c
+  first f = bimap f id
 
-    second :: (b -> c) -> p a b -> p a c
-    second = bimap id
+  second :: (b -> c) -> p a b -> p a c
+  second = bimap id
 
 instance Bifunctor (,) where
-    bimap f g ~(a, b) = (f a, g b)
+  bimap f g ~(a, b) = (f a, g b)
 
 instance Bifunctor ((,,) x1) where
-    bimap f g ~(x1, a, b) = (x1, f a, g b)
+  bimap f g ~(x1, a, b) = (x1, f a, g b)
 
 instance Bifunctor ((,,,) x1 x2) where
-    bimap f g ~(x1, x2, a, b) = (x1, x2, f a, g b)
+  bimap f g ~(x1, x2, a, b) = (x1, x2, f a, g b)
 
 instance Bifunctor ((,,,,) x1 x2 x3) where
-    bimap f g ~(x1, x2, x3, a, b) = (x1, x2, x3, f a, g b)
+  bimap f g ~(x1, x2, x3, a, b) = (x1, x2, x3, f a, g b)
 
 instance Bifunctor ((,,,,,) x1 x2 x3 x4) where
-    bimap f g ~(x1, x2, x3, x4, a, b) = (x1, x2, x3, x4, f a, g b)
+  bimap f g ~(x1, x2, x3, x4, a, b) = (x1, x2, x3, x4, f a, g b)
 
 instance Bifunctor ((,,,,,,) x1 x2 x3 x4 x5) where
-    bimap f g ~(x1, x2, x3, x4, x5, a, b) = (x1, x2, x3, x4, x5, f a, g b)
+  bimap f g ~(x1, x2, x3, x4, x5, a, b) = (x1, x2, x3, x4, x5, f a, g b)
 
 instance Bifunctor Either where
-    bimap f _ (Left a) = Left (f a)
-    bimap _ g (Right b) = Right (g b)
+  bimap f _ (Left a) = Left (f a)
+  bimap _ g (Right b) = Right (g b)
 
 instance Bifunctor Const where
-    bimap f _ (Const a) = Const (f a)
+  bimap f _ (Const a) = Const (f a)
diff --git a/src/Debug.hs b/src/Debug.hs
--- a/src/Debug.hs
+++ b/src/Debug.hs
@@ -12,7 +12,10 @@
   notImplemented,
 ) where
 
-import qualified Prelude as P
+import Data.String (String)
+import Control.Monad (Monad, return)
+
+import qualified Base as P
 import qualified Debug.Trace as T
 
 {-# WARNING undefined "'undefined' remains in code" #-}
@@ -20,27 +23,27 @@
 undefined = P.undefined
 
 {-# WARNING error "'error' remains in code" #-}
-error :: P.String -> a
+error :: String -> a
 error = P.error
 
 {-# WARNING trace "'trace' remains in code" #-}
-trace :: P.String -> a -> a
+trace :: String -> a -> a
 trace = T.trace
 
 {-# WARNING traceShow "'traceShow' remains in code" #-}
-traceShow :: P.Show a => a -> a
-traceShow a = T.trace (P.show a) a
+traceShow :: P.Show a => a -> b -> b
+traceShow a b = T.trace (P.show a) b
 
 {-# WARNING traceShowM "'traceShowM' remains in code" #-}
-traceShowM :: (P.Show a, P.Monad m) => a -> m ()
+traceShowM :: (P.Show a, Monad m) => a -> m ()
 traceShowM a = traceM (P.show a)
 
 {-# WARNING traceM "'traceM' remains in code" #-}
-traceM :: (P.Monad m) => P.String -> m ()
-traceM s = T.trace s (P.return ())
+traceM :: (Monad m) => String -> m ()
+traceM s = T.trace s (return ())
 
 {-# WARNING traceIO "'traceIO' remains in code" #-}
-traceIO :: P.String -> P.IO ()
+traceIO :: String -> P.IO ()
 traceIO = T.traceIO
 
 {-# WARNING notImplemented "'notImplemented' remains in code" #-}
diff --git a/src/Protolude.hs b/src/Protolude.hs
--- a/src/Protolude.hs
+++ b/src/Protolude.hs
@@ -33,6 +33,8 @@
   , putStrLn
   , print
   , show
+  , error
+  , undefined
   )
 import qualified Base as PBase
 
@@ -51,8 +53,6 @@
   , tailSafe
   , lastDef
   , lastMay
-  , lookupJust
-  , findJust
   , foldr1May
   , foldl1May
   , atMay
@@ -80,7 +80,7 @@
     foldr1
   , foldl1
   )
-import Data.Semiring as X
+import Semiring as X
 import Data.Functor.Identity as X
 
 #if ( __GLASGOW_HASKELL__ >= 800 )
diff --git a/src/Semiring.hs b/src/Semiring.hs
new file mode 100644
--- /dev/null
+++ b/src/Semiring.hs
@@ -0,0 +1,19 @@
+{-# LANGUAGE Safe #-}
+{-# LANGUAGE NoImplicitPrelude #-}
+
+module Semiring (
+  Semiring(..),
+  zero,
+) where
+
+import Data.Monoid
+
+-- | Alias for 'mempty'
+zero :: Monoid m => m
+zero = mempty
+
+class Monoid m => Semiring m where
+  {-# MINIMAL one, (<.>) #-}
+
+  one :: m
+  (<.>) :: m -> m -> m