diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,13 @@
+## Megaparsec 5.0.1
+
+* Derived `NFData` instances for `Pos`, `InvalidPosException`, `SourcePos`,
+  `ErrorItem`, `Dec`, `ParseError`, and `State`.
+
+* Derived `Data` instance for `ParseError`, `Data` and `Typeable` instances
+  for `SourcePos` and `State`.
+
+* Minor documentation improvements.
+
 ## Megaparsec 5.0.0
 
 ### General changes
@@ -44,6 +54,9 @@
 
 * `unexpected` combinator now accepts argument of type `ErrorItem` instead
   of plain `String`.
+
+* General performance improvements and improvements in speed of some
+  combinators, `manyTill` in particular.
 
 ### Error messages
 
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@
 * [Features](#features)
     * [Core features](#core-features)
     * [Error messages](#error-messages)
-    * [Alex/Happy support](#alex/happy-support)
+    * [Alex and Happy support](#alex-and-happy-support)
     * [Character parsing](#character-parsing)
     * [Permutation parsing](#permutation-parsing)
     * [Expression parsing](#expression-parsing)
@@ -122,7 +122,7 @@
 messages for indentation-sensitive parsing instead of plain “incorrect
 indentation” phrase.
 
-### Alex/Happy support
+### Alex and Happy support
 
 Megaparsec works well with streams of tokens produced by tools like
 Alex/Happy. Megaparsec 5 adds `updatePos` method to `Stream` type class that
diff --git a/Text/Megaparsec/Error.hs b/Text/Megaparsec/Error.hs
--- a/Text/Megaparsec/Error.hs
+++ b/Text/Megaparsec/Error.hs
@@ -14,6 +14,7 @@
 
 {-# LANGUAGE CPP                #-}
 {-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE DeriveGeneric      #-}
 {-# LANGUAGE FlexibleContexts   #-}
 {-# LANGUAGE FlexibleInstances  #-}
 
@@ -28,6 +29,7 @@
   , sourcePosStackPretty )
 where
 
+import Control.DeepSeq
 import Control.Monad.Catch
 import Data.Data (Data)
 import Data.Foldable (concat)
@@ -36,6 +38,7 @@
 import Data.Semigroup
 import Data.Set (Set)
 import Data.Typeable (Typeable)
+import GHC.Generics
 import Prelude hiding (concat)
 import qualified Data.List.NonEmpty as NE
 import qualified Data.Set           as E
@@ -55,8 +58,10 @@
   = Tokens (NonEmpty t)      -- ^ Non-empty stream of tokens
   | Label (NonEmpty Char)    -- ^ Label (cannot be empty)
   | EndOfInput               -- ^ End of input
-  deriving (Show, Read, Eq, Ord, Data, Typeable)
+  deriving (Show, Read, Eq, Ord, Data, Typeable, Generic)
 
+instance NFData t => NFData (ErrorItem t)
+
 -- | The type class defines how to represent information about various
 -- exceptional situations. Data types that are used as custom data component
 -- in 'ParseError' must be instances of this type class.
@@ -88,9 +93,16 @@
 
 data Dec
   = DecFail String         -- ^ 'fail' has been used in parser monad
-  | DecIndentation Ordering Pos Pos -- ^ Incorrect indentation error
+  | DecIndentation Ordering Pos Pos
+    -- ^ Incorrect indentation error: desired ordering between reference
+    -- level and actual level, reference indentation level, actual
+    -- indentation level
   deriving (Show, Read, Eq, Ord, Data, Typeable)
 
+instance NFData Dec where
+  rnf (DecFail str) = rnf str
+  rnf (DecIndentation ord ref act) = ord `seq` rnf ref `seq` rnf act
+
 instance ErrorComponent Dec where
   representFail        = DecFail
   representIndentation = DecIndentation
@@ -114,7 +126,9 @@
   , errorUnexpected :: Set (ErrorItem t)  -- ^ Unexpected items
   , errorExpected   :: Set (ErrorItem t)  -- ^ Expected items
   , errorCustom     :: Set e              -- ^ Associated data, if any
-  } deriving (Show, Read, Eq, Typeable)
+  } deriving (Show, Read, Eq, Data, Typeable, Generic)
+
+instance (NFData t, NFData e) => NFData (ParseError t e)
 
 instance (Ord t, Ord e) => Semigroup (ParseError t e) where
   (<>) = mergeError
diff --git a/Text/Megaparsec/Lexer.hs b/Text/Megaparsec/Lexer.hs
--- a/Text/Megaparsec/Lexer.hs
+++ b/Text/Megaparsec/Lexer.hs
@@ -81,7 +81,7 @@
 --
 -- @spaceChar@ is used to parse trivial space characters. You can use
 -- 'C.spaceChar' from "Text.Megaparsec.Char" for this purpose as well as
--- your own parser (if you don't want automatically consume newlines, for
+-- your own parser (if you don't want to automatically consume newlines, for
 -- example).
 --
 -- @lineComment@ is used to parse line comments. You can use
diff --git a/Text/Megaparsec/Pos.hs b/Text/Megaparsec/Pos.hs
--- a/Text/Megaparsec/Pos.hs
+++ b/Text/Megaparsec/Pos.hs
@@ -11,9 +11,11 @@
 -- and column number. List of such positions can be used to model stack of
 -- include files.
 
-{-# LANGUAGE CPP                #-}
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE TupleSections      #-}
+{-# LANGUAGE CPP                        #-}
+{-# LANGUAGE DeriveDataTypeable         #-}
+{-# LANGUAGE DeriveGeneric              #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE TupleSections              #-}
 
 module Text.Megaparsec.Pos
   ( -- * Abstract position
@@ -31,10 +33,12 @@
   , defaultTabWidth )
 where
 
+import Control.DeepSeq
 import Control.Monad.Catch
 import Data.Data (Data)
 import Data.Semigroup
 import Data.Typeable (Typeable)
+import GHC.Generics
 import Unsafe.Coerce
 
 #if !MIN_VERSION_base(4,8,0)
@@ -52,7 +56,7 @@
 -- @since 5.0.0
 
 newtype Pos = Pos Word
-  deriving (Show, Eq, Ord, Data, Typeable)
+  deriving (Show, Eq, Ord, Data, Typeable, NFData)
 
 -- | Construction of 'Pos' from an instance of 'Integral'. The function
 -- throws 'InvalidPosException' when given non-positive argument. Note that
@@ -105,9 +109,10 @@
 -- @since 5.0.0
 
 data InvalidPosException = InvalidPosException
-  deriving (Eq, Show, Data, Typeable)
+  deriving (Eq, Show, Data, Typeable, Generic)
 
 instance Exception InvalidPosException
+instance NFData    InvalidPosException
 
 ----------------------------------------------------------------------------
 -- Source position
@@ -121,14 +126,17 @@
   { sourceName   :: FilePath -- ^ Name of source file
   , sourceLine   :: !Pos     -- ^ Line number
   , sourceColumn :: !Pos     -- ^ Column number
-  } deriving (Show, Read, Eq, Ord)
+  } deriving (Show, Read, Eq, Ord, Data, Typeable, Generic)
 
+instance NFData SourcePos
+
 -- | Construct initial position (line 1, column 1) given name of source
 -- file.
 
 initialPos :: String -> SourcePos
 initialPos n = SourcePos n u u
   where u = unsafePos 1
+{-# INLINE initialPos #-}
 
 -- | Pretty-print a 'SourcePos'.
 --
diff --git a/Text/Megaparsec/Prim.hs b/Text/Megaparsec/Prim.hs
--- a/Text/Megaparsec/Prim.hs
+++ b/Text/Megaparsec/Prim.hs
@@ -13,6 +13,8 @@
 
 {-# LANGUAGE BangPatterns               #-}
 {-# LANGUAGE CPP                        #-}
+{-# LANGUAGE DeriveDataTypeable         #-}
+{-# LANGUAGE DeriveGeneric              #-}
 {-# LANGUAGE FlexibleContexts           #-}
 {-# LANGUAGE FlexibleInstances          #-}
 {-# LANGUAGE FunctionalDependencies     #-}
@@ -55,6 +57,7 @@
   , parseTest )
 where
 
+import Control.DeepSeq
 import Control.Monad
 import Control.Monad.Cont.Class
 import Control.Monad.Error.Class
@@ -63,12 +66,15 @@
 import Control.Monad.State.Class hiding (state)
 import Control.Monad.Trans
 import Control.Monad.Trans.Identity
+import Data.Data (Data)
 import Data.Foldable (foldl')
 import Data.List.NonEmpty (NonEmpty (..))
 import Data.Monoid hiding ((<>))
 import Data.Proxy
 import Data.Semigroup
 import Data.Set (Set)
+import Data.Typeable (Typeable)
+import GHC.Generics
 import Prelude hiding (all)
 import qualified Control.Applicative               as A
 import qualified Control.Monad.Fail                as Fail
@@ -100,8 +106,10 @@
   { stateInput    :: s
   , statePos      :: NonEmpty SourcePos
   , stateTabWidth :: Pos }
-  deriving (Show, Eq)
+  deriving (Show, Eq, Data, Typeable, Generic)
 
+instance NFData s => NFData (State s)
+
 -- | All information available after parsing. This includes consumption of
 -- input, success (with returned value) or failure (with parse error), and
 -- parser state at the end of parsing.
@@ -367,7 +375,7 @@
 manyErr :: a
 manyErr = error $
   "Text.Megaparsec.Prim.many: combinator 'many' is applied to a parser"
-  ++ " that accepts an empty string."
+  ++ " that may consume no input."
 
 instance (ErrorComponent e, Stream s)
     => Monad (ParsecT e s m) where
diff --git a/megaparsec.cabal b/megaparsec.cabal
--- a/megaparsec.cabal
+++ b/megaparsec.cabal
@@ -27,7 +27,7 @@
 -- POSSIBILITY OF SUCH DAMAGE.
 
 name:                 megaparsec
-version:              5.0.0
+version:              5.0.1
 cabal-version:        >= 1.10
 license:              BSD2
 license-file:         LICENSE.md
@@ -56,14 +56,15 @@
   default:            False
 
 library
-  build-depends:      base         >= 4.6 && < 5
-                    , bytestring
-                    , containers   >= 0.5 && < 0.6
-                    , exceptions   >= 0.6 && < 0.9
-                    , mtl          == 2.*
+  build-depends:      base         >= 4.6   && < 5.0
+                    , bytestring   >= 0.2   && < 0.11
+                    , containers   >= 0.5   && < 0.6
+                    , deepseq      >= 1.3   && < 1.5
+                    , exceptions   >= 0.6   && < 0.9
+                    , mtl          >= 2.0   && < 3.0
                     , scientific   >= 0.3.1 && < 0.4
-                    , text         >= 0.2
-                    , transformers >= 0.4 && < 0.6
+                    , text         >= 0.2   && < 1.3
+                    , transformers >= 0.4   && < 0.6
 
   if !impl(ghc >= 8.0)
     -- packages providing modules that moved into base-4.9.0.0
@@ -88,7 +89,7 @@
                     , Text.Megaparsec.Text
                     , Text.Megaparsec.Text.Lazy
   if flag(dev)
-    ghc-options:      -Wall
+    ghc-options:      -Wall -Werror
     if impl(ghc >= 8.0)
       ghc-options:    -Wcompat
       ghc-options:    -Wnoncanonical-monadfail-instances
@@ -102,7 +103,7 @@
   hs-source-dirs:     old-tests
   type:               exitcode-stdio-1.0
   if flag(dev)
-    ghc-options:      -Wall
+    ghc-options:      -Wall -Werror
   else
     ghc-options:      -O2 -Wall
   other-modules:      Bugs
@@ -112,10 +113,10 @@
                     , Bugs.Bug35
                     , Bugs.Bug39
                     , Util
-  build-depends:      base                 >= 4.6 && < 5
+  build-depends:      base                 >= 4.6 && < 5.0
                     , HUnit                >= 1.2 && < 1.4
-                    , megaparsec           >= 5.0.0
-                    , test-framework       >= 0.6 && < 1
+                    , megaparsec           >= 5.0.1
+                    , test-framework       >= 0.6 && < 1.0
                     , test-framework-hunit >= 0.2 && < 0.4
   default-language:   Haskell2010
 
@@ -124,7 +125,7 @@
   hs-source-dirs:     tests
   type:               exitcode-stdio-1.0
   if flag(dev)
-    ghc-options:      -Wall
+    ghc-options:      -Wall -Werror
   else
     ghc-options:      -O2 -Wall
   other-modules:      Char
@@ -136,20 +137,20 @@
                     , Pos
                     , Prim
                     , Util
-  build-depends:      base           >= 4.6 && < 5
-                    , HUnit          >= 1.2 && < 1.4
-                    , QuickCheck     >= 2.8.2 && < 3
-                    , bytestring
-                    , containers     >= 0.5 && < 0.6
-                    , exceptions     >= 0.6 && < 0.9
-                    , megaparsec     >= 5.0.0
-                    , mtl            == 2.*
+  build-depends:      base           >= 4.6   && < 5.0
+                    , HUnit          >= 1.2   && < 1.4
+                    , QuickCheck     >= 2.8.2 && < 3.0
+                    , bytestring     >= 0.2   && < 0.11
+                    , containers     >= 0.5   && < 0.6
+                    , exceptions     >= 0.6   && < 0.9
+                    , megaparsec     >= 5.0.1
+                    , mtl            >= 2.0   && < 3.0
                     , scientific     >= 0.3.1 && < 0.4
-                    , test-framework >= 0.6 && < 1
+                    , test-framework >= 0.6   && < 1.0
                     , test-framework-hunit       >= 0.3 && < 0.4
                     , test-framework-quickcheck2 >= 0.3 && < 0.4
-                    , text           >= 0.2
-                    , transformers   >= 0.4 && < 0.6
+                    , text           >= 0.2   && < 1.3
+                    , transformers   >= 0.4   && < 0.6
 
   if !impl(ghc >= 8.0)
     -- packages providing modules that moved into base-4.9.0.0
@@ -165,14 +166,14 @@
   hs-source-dirs:     benchmarks
   type:               exitcode-stdio-1.0
   if flag(dev)
-    ghc-options:      -O2 -Wall
+    ghc-options:      -O2 -Wall -Werror
   else
     ghc-options:      -O2 -Wall
-  build-depends:      base       >= 4.6 && < 5
-                    , bytestring >= 0.10 && < 2
+  build-depends:      base       >= 4.6  && < 5.0
+                    , bytestring >= 0.10 && < 0.11
                     , criterion  >= 0.6.2.1 && < 1.2
-                    , megaparsec >= 5.0.0
-                    , text       >= 0.2
+                    , megaparsec >= 5.0.1
+                    , text       >= 0.2  && < 1.3
   default-language:   Haskell2010
 
 source-repository head