diff --git a/spatial-math.cabal b/spatial-math.cabal
--- a/spatial-math.cabal
+++ b/spatial-math.cabal
@@ -1,5 +1,5 @@
 name:                spatial-math
-version:             0.2.2.0
+version:             0.2.3.0
 synopsis:            3d math including quaternions/euler angles/dcms and utility functions
 description:         This is a port of my 'mathlib' C library: `https://github.com/ghorn/mathlib`
 license:             BSD3
diff --git a/src/SpatialMathT.hs b/src/SpatialMathT.hs
--- a/src/SpatialMathT.hs
+++ b/src/SpatialMathT.hs
@@ -33,7 +33,7 @@
 newtype V3T f a = V3T {unV :: V3 a}
                 deriving ( Functor, Foldable, Traversable
                          , Applicative
-                         , Additive, Storable
+                         , Additive, Metric, Storable
                          , Num, Fractional, Eq, Show, Ord
                          , Generic1, Generic
                          , Serialize, Binary