diff --git a/cdar-mBound.cabal b/cdar-mBound.cabal
--- a/cdar-mBound.cabal
+++ b/cdar-mBound.cabal
@@ -2,7 +2,7 @@
 -- see http://haskell.org/cabal/users-guide/
 
 name:                cdar-mBound
-version:             0.1.0.1
+version:             0.1.0.2
 synopsis:            Exact real arithmetic using Centred Dyadic Approximations
 description:         Please see https://github.com/michalkonecny/cdar/tree/mBound#readme
 license:             BSD3
diff --git a/src/Data/CDAR/Approx.hs b/src/Data/CDAR/Approx.hs
--- a/src/Data/CDAR/Approx.hs
+++ b/src/Data/CDAR/Approx.hs
@@ -898,7 +898,7 @@
         -- limitAndBoundMB mb $ 
         x * sqrtRecA k x
     where
-    k = 2*mb + 2
+    k = mb + 2
 
 {-|
 This uses Newton's method for computing the reciprocal of the square root.