diff --git a/QuickCheck.cabal b/QuickCheck.cabal
--- a/QuickCheck.cabal
+++ b/QuickCheck.cabal
@@ -1,5 +1,5 @@
 Name: QuickCheck
-Version: 2.12.5
+Version: 2.12.6
 Cabal-Version: >= 1.8
 Build-type: Simple
 License: BSD3
@@ -55,7 +55,7 @@
 source-repository this
   type:     git
   location: https://github.com/nick8325/quickcheck
-  tag:      2.12.5
+  tag:      2.12.6
 
 flag templateHaskell
   Description: Build Test.QuickCheck.All, which uses Template Haskell.
diff --git a/Test/QuickCheck/Arbitrary.hs b/Test/QuickCheck/Arbitrary.hs
--- a/Test/QuickCheck/Arbitrary.hs
+++ b/Test/QuickCheck/Arbitrary.hs
@@ -1035,8 +1035,15 @@
   sized $ \s ->
     do let bits n | n == 0 = 0
                   | otherwise = 1 + bits (n `quot` 2)
-           k  = 2^(s*(bits mn `max` bits mx `max` 40) `div` 80)
-       n <- choose (toInteger mn `max` (-k), toInteger mx `min` k)
+           k = (toInteger s*(bits mn `max` bits mx `max` 40) `div` 80)
+           -- computes x `min` (2^k), but avoids computing 2^k
+           -- if it is too large
+           x `minexp` k
+             | bits x < k = x
+             | otherwise = x `min` (2^k)
+           -- x `max` (-2^k)
+           x `maxexpneg` k = -((-x) `minexp` k)
+       n <- choose (toInteger mn `maxexpneg` k, toInteger mx `minexp` k)
        return (fromInteger n)
 
 -- ** Generators for various kinds of character
diff --git a/Test/QuickCheck/Gen.hs b/Test/QuickCheck/Gen.hs
--- a/Test/QuickCheck/Gen.hs
+++ b/Test/QuickCheck/Gen.hs
@@ -123,6 +123,14 @@
 scale :: (Int -> Int) -> Gen a -> Gen a
 scale f g = sized (\n -> resize (f n) g)
 
+-- | Increase the size parameter by a factor of 2.
+larger :: Gen a -> Gen a
+larger = scale (*2)
+
+-- | Decrease the size parameter by a factor of 2.
+smaller :: Gen a -> Gen a
+smaller = scale (`div` 2)
+
 -- | Generates a random element in the given inclusive range.
 choose :: Random a => (a,a) -> Gen a
 choose rng = MkGen (\r _ -> let (x,_) = randomR rng r in x)
diff --git a/Test/QuickCheck/Modifiers.hs b/Test/QuickCheck/Modifiers.hs
--- a/Test/QuickCheck/Modifiers.hs
+++ b/Test/QuickCheck/Modifiers.hs
@@ -58,6 +58,8 @@
   , NonNegative(..)
   , Large(..)
   , Small(..)
+  , Larger(..)
+  , Smaller(..)
   , Smart(..)
   , Shrink2(..)
 #ifndef NO_MULTI_PARAM_TYPE_CLASSES
@@ -344,8 +346,8 @@
   shrink (Large x) = fmap Large (shrinkIntegral x)
 
 --------------------------------------------------------------------------
--- | @Small x@: generates values of @x@ drawn from a small range.
--- The opposite of 'Large'.
+-- | @Small x@: generates values of the integral type @x@ drawn from a
+-- small range.  The opposite of 'Large'.
 newtype Small a = Small {getSmall :: a}
  deriving ( Eq, Ord, Show, Read
 #ifndef NO_NEWTYPE_DERIVING
@@ -362,6 +364,23 @@
 instance Integral a => Arbitrary (Small a) where
   arbitrary = fmap Small arbitrarySizedIntegral
   shrink (Small x) = map Small (shrinkIntegral x)
+
+--------------------------------------------------------------------------
+-- | @Larger x@: doubles the QuickCheck size parameter used when
+-- generating @x@.
+newtype Larger a = Larger {getLarger :: a}
+ deriving ( Eq, Ord, Show, Read
+#ifndef NO_TYPEABLE
+          , Typeable
+#endif
+          )
+
+instance Functor Larger where
+  fmap f (Larger x) = Larger (f x)
+
+instance Arbitrary a => Arbitrary (Larger a) where
+  arbitrary = larger arbitrary
+  shrink (Larger x) = map Larger (shrink x)
 
 --------------------------------------------------------------------------
 -- | @Shrink2 x@: allows 2 shrinking steps at the same time when shrinking x
diff --git a/changelog b/changelog
--- a/changelog
+++ b/changelog
@@ -1,3 +1,13 @@
+QuickCheck 2.12.6 (released 2018-10-02)
+	* Make arbitrarySizedBoundedIntegral handle huge sizes correctly.
+	* Add changelog for QuickCheck 2.12.5 :)
+
+QuickCheck 2.12.5 (released 2018-09-30)
+	* Export isSuccess from Test.QuickCheck.
+	* Export CoArbitrary even when generics are disabled (bugfix).
+	* Fix bug in shrinkDecimal.
+	* Include Test.QuickCheck.Gen in exposed modules for Haddock.
+
 QuickCheck 2.12.3, 2.12.4 (released 2018-09-12)
 	* Shrinking for Float and Decimal now works by reducing the number
 	  of digits in the number. The new function shrinkDecimal