diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,13 @@
+## [v1.4.2.1](https://github.com/diagrams/diagrams-lib/tree/v1.4.2.1) (2018-04-13)
+
+- Allow `base-4.11` (GHC 8.4)
+- Allow `tasty-quickcheck-0.10`
+- Bug fix for `Diagrams.TwoD.Offset.capArc` ([#310](https://github.com/diagrams/diagrams-lib/pull/310))
+
+## [v1.4.2-r1](https://github.com/diagrams/diagrams-lib/tree/v1.4.2-r1) (2017-12-20)
+
+Hackage revision to allow `tasty-1.0` in the test suite.
+
 ## [v1.4.2](https://github.com/diagrams/diagrams-lib/tree/v1.4.2) (2017-12-20)
 
 - New functions:
diff --git a/diagrams-lib.cabal b/diagrams-lib.cabal
--- a/diagrams-lib.cabal
+++ b/diagrams-lib.cabal
@@ -1,5 +1,5 @@
 Name:                diagrams-lib
-Version:             1.4.2
+Version:             1.4.2.1
 Synopsis:            Embedded domain-specific language for declarative graphics
 Description:         Diagrams is a flexible, extensible EDSL for creating
                      graphics of many types.  Graphics can be created
@@ -18,10 +18,10 @@
 Bug-reports:         http://github.com/diagrams/diagrams-lib/issues
 Category:            Graphics
 Build-type:          Simple
-Cabal-version:       >=1.18
+Cabal-version:       1.18
 Extra-source-files:  CHANGELOG.md, README.markdown, diagrams/*.svg
 Extra-doc-files:     diagrams/*.svg
-Tested-with:         GHC == 7.6.3, GHC == 7.8.4, GHC == 7.10.2, GHC == 8.0.1, GHC == 8.2.2
+Tested-with:         GHC == 7.8.4, GHC == 7.10.2, GHC == 8.0.1, GHC == 8.2.2, GHC == 8.4.1
 Source-repository head
   type:     git
   location: http://github.com/diagrams/diagrams-lib.git
@@ -100,7 +100,7 @@
                        Diagrams.TwoD.Types,
                        Diagrams.TwoD.Vector,
                        Diagrams.Util
-  Build-depends:       base >= 4.6 && < 4.11,
+  Build-depends:       base >= 4.6 && < 4.12,
                        containers >= 0.3 && < 0.6,
                        array >= 0.3 && < 0.6,
                        semigroups >= 0.3.4 && < 0.19,
@@ -113,7 +113,7 @@
                        data-default-class < 0.2,
                        fingertree >= 0.1 && < 0.2,
                        intervals >= 0.7 && < 0.9,
-                       lens >= 4.6 && < 4.16,
+                       lens >= 4.6 && < 4.17,
                        tagged >= 0.7,
                        optparse-applicative >= 0.11 && < 0.15,
                        filepath,
@@ -158,9 +158,9 @@
                , Instances
   hs-source-dirs: test
   build-depends:       base,
-                       tasty >= 0.10 && < 0.13,
+                       tasty >= 0.10 && < 1.1,
                        tasty-hunit >= 0.9.2 && < 0.11,
-                       tasty-quickcheck >= 0.8 && < 0.10,
+                       tasty-quickcheck >= 0.8 && < 0.11,
                        deepseq >= 1.3 && < 1.5,
                        diagrams-lib,
                        lens,
diff --git a/src/Diagrams/Animation.hs b/src/Diagrams/Animation.hs
--- a/src/Diagrams/Animation.hs
+++ b/src/Diagrams/Animation.hs
@@ -50,7 +50,7 @@
 
 -- | A value of type @QAnimation b v m@ is an animation (a
 --   time-varying diagram with start and end times) that can be
---   rendered by backspace @b@, with vector space @v@ and monoidal
+--   rendered by backend @b@, with vector space @v@ and monoidal
 --   annotations of type @m@.
 type QAnimation b v n m = Active (QDiagram b v n m)
 
diff --git a/src/Diagrams/Trail.hs b/src/Diagrams/Trail.hs
--- a/src/Diagrams/Trail.hs
+++ b/src/Diagrams/Trail.hs
@@ -174,7 +174,7 @@
 --   beginning which have a combined arc length of at least 5).
 
 newtype SegTree v n = SegTree (FingerTree (SegMeasure v n) (Segment Closed v n))
-  deriving (Eq, Ord, Show, Monoid, Transformable, FT.Measured (SegMeasure v n))
+  deriving (Eq, Ord, Show, Monoid, Semigroup, Transformable, FT.Measured (SegMeasure v n))
 
 instance Wrapped (SegTree v n) where
   type Unwrapped (SegTree v n) = FingerTree (SegMeasure v n) (Segment Closed v n)
diff --git a/src/Diagrams/TwoD/Offset.hs b/src/Diagrams/TwoD/Offset.hs
--- a/src/Diagrams/TwoD/Offset.hs
+++ b/src/Diagrams/TwoD/Offset.hs
@@ -470,8 +470,8 @@
 capArc :: RealFloat n => n -> Point V2 n -> Point V2 n -> Point V2 n -> Trail V2 n
 capArc r c a b = trailLike . moveTo c $ fs
   where
-    fs | r < 0     = scale (-r) $ arcCW  (dirBetween a c) (dirBetween b c)
-       | otherwise = scale r    $ arcCCW (dirBetween a c) (dirBetween b c)
+    fs | r < 0     = scale (-r) $ arcCW  (dirBetween c a) (dirBetween c b)
+       | otherwise = scale r    $ arcCCW (dirBetween c a) (dirBetween c b)
 
 -- | Join together a list of located trails with the given join style.  The
 --   style is given as a function to compute the join given the local information