diff --git a/CHANGES b/CHANGES
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,8 @@
+0.1.0.7 (27 September 2013)
+---------------------------
+
+  * allow semigroups-0.11
+
 0.1.0.6 (16 July 2013)
 ----------------------
 
diff --git a/active.cabal b/active.cabal
--- a/active.cabal
+++ b/active.cabal
@@ -1,5 +1,5 @@
 name:                active
-version:             0.1.0.6
+version:             0.1.0.7
 synopsis:            Abstractions for animation
 description:         "Active" abstraction for animated things with finite start and end times.
 license:             BSD3
@@ -21,7 +21,7 @@
   exposed-modules:     Data.Active
   build-depends:       base >= 4.0 && < 4.8,
                        array >= 0.3 && < 0.5,
-                       semigroups >= 0.1 && < 0.10,
+                       semigroups >= 0.1 && < 0.12,
                        semigroupoids >= 1.2 && < 3.2,
                        vector-space >= 0.8 && < 0.9,
                        newtype >= 0.2 && < 0.3
@@ -33,7 +33,7 @@
     main-is:           active-tests.hs
     build-depends:     base >= 4.0 && < 4.8,
                        array >= 0.3 && < 0.5,
-                       semigroups >= 0.1 && < 0.10,
+                       semigroups >= 0.1 && < 0.12,
                        semigroupoids >= 1.2 && < 3.2,
                        vector-space >= 0.8 && < 0.9,
                        newtype >= 0.2 && < 0.3,
diff --git a/src/Data/Active.hs b/src/Data/Active.hs
--- a/src/Data/Active.hs
+++ b/src/Data/Active.hs
@@ -144,6 +144,7 @@
 import Data.Monoid (First(..))
 
 import Data.VectorSpace hiding ((<.>))
+import qualified Data.VectorSpace as VS
 import Data.AffineSpace
 
 ------------------------------------------------------------
@@ -157,7 +158,7 @@
 --   other numeric types.
 newtype Time = Time { unTime :: Rational }
   deriving ( Eq, Ord, Show, Read, Enum, Num, Fractional, Real, RealFrac
-           , AdditiveGroup, InnerSpace
+           , AdditiveGroup
            )
 
 instance Newtype Time Rational where
@@ -167,6 +168,9 @@
 instance VectorSpace Time where
   type Scalar Time = Rational
   s *^ (Time t) = Time (s * t)
+
+instance InnerSpace Time where
+  (Time a) <.> (Time b) = a * b
 
 -- | Convert any value of a 'Real' type (including @Int@, @Integer@,
 --   @Rational@, @Float@, and @Double@) to a 'Time'.