diff --git a/CHANGELOG.markdown b/CHANGELOG.markdown
--- a/CHANGELOG.markdown
+++ b/CHANGELOG.markdown
@@ -1,3 +1,7 @@
+1.9.1
+-----
+* Added a role annotation to `V n a` to prevent users from using GHC 7.8's `Coercible` machinery to violate invariants.
+
 1.9.0.1
 -----
 * Fixed a broken build
diff --git a/linear.cabal b/linear.cabal
--- a/linear.cabal
+++ b/linear.cabal
@@ -1,6 +1,6 @@
 name:          linear
 category:      Math, Algebra
-version:       1.9.0.1
+version:       1.9.1
 license:       BSD3
 cabal-version: >= 1.8
 license-file:  LICENSE
diff --git a/src/Linear/V.hs b/src/Linear/V.hs
--- a/src/Linear/V.hs
+++ b/src/Linear/V.hs
@@ -9,6 +9,7 @@
 #if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 707
 {-# LANGUAGE DataKinds #-}
 {-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE RoleAnnotations #-}
 #define USE_TYPE_LITS 1
 #endif
 #if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 702
@@ -74,6 +75,10 @@
 class Dim n where
   reflectDim :: p n -> Int
 
+#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 707
+type role V nominal representational
+#endif
+
 newtype V n a = V { toVector :: V.Vector a } deriving (Eq,Ord,Show,Read
 #if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 702
                                                       ,Generic
@@ -83,7 +88,6 @@
                                                       ,Generic1
 #endif
                                                       )
-
 dim :: forall n a. Dim n => V n a -> Int
 dim _ = reflectDim (Proxy :: Proxy n)
 {-# INLINE dim #-}