diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+# 0.6.2.1
+
+- Support quickcheck-instances-0.3.12 (tests)
+
 # 0.6.2.0
 
 - Add support to bifunctors-5.1
diff --git a/test/Tests.hs b/test/Tests.hs
--- a/test/Tests.hs
+++ b/test/Tests.hs
@@ -1,4 +1,5 @@
 {-# OPTIONS_GHC -fno-warn-orphans #-}
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE KindSignatures #-}
@@ -172,9 +173,11 @@
 
 instance (CoArbitrary a, CoArbitrary b) => CoArbitrary (These a b)
 
+#if !MIN_VERSION_quickcheck_instances(0,3,12)
 instance Arbitrary a => Arbitrary (V.Vector a) where
   arbitrary = V.fromList <$> arbitrary
   shrink = fmap V.fromList . shrink . V.toList
+#endif
 
 instance Arbitrary a => Arbitrary (ZipList a) where
   arbitrary = ZipList <$> arbitrary
diff --git a/these.cabal b/these.cabal
--- a/these.cabal
+++ b/these.cabal
@@ -1,5 +1,5 @@
 Name:                these
-Version:             0.6.2.0
+Version:             0.6.2.1
 Synopsis:            An either-or-both data type & a generalized 'zip with padding' typeclass
 Homepage:            https://github.com/isomorphism/these
 License:             BSD3
@@ -36,13 +36,13 @@
   Build-depends:       base                     >= 4.4   && < 5,
                        containers               >= 0.4   && < 0.6,
                        mtl                      >= 2     && < 2.3,
-                       transformers             >= 0.2   && < 0.5,
+                       transformers             >= 0.2   && < 0.6,
                        semigroups               >= 0.8   && < 0.19,
-                       bifunctors               >= 0.1   && < 5.2,
+                       bifunctors               >= 0.1   && < 5.3,
                        semigroupoids            >= 1.0   && < 5.1,
-                       profunctors              >= 3     && < 5.2,
+                       profunctors              >= 3     && < 5.3,
                        vector                   >= 0.4   && < 0.12,
-                       transformers-compat      >= 0.2   && < 0.5,
+                       transformers-compat      >= 0.2   && < 0.6,
                        hashable                 >= 1.2.3 && < 1.3,
                        unordered-containers     >= 0.2   && < 0.3,
                        data-default-class       >= 0.0   && < 0.1
@@ -56,14 +56,14 @@
   hs-source-dirs:      test
   ghc-options:         -Wall
   build-depends:       these,
-                       base                   >= 4.5   && < 4.9,
-                       transformers           >= 0.2   && < 0.5,
+                       base                   >= 4.5   && < 4.10,
+                       transformers           >= 0.2   && < 0.6,
                        vector                 >= 0.4   && < 0.12,
-                       bifunctors             >= 0.1   && < 5.2,
+                       bifunctors             >= 0.1   && < 5.3,
                        containers             >= 0.4   && < 0.6,
                        hashable               >= 1.2.3 && < 1.3,
                        unordered-containers   >= 0.2   && < 0.3,
                        tasty                  >= 0.10  && < 0.12,
                        tasty-quickcheck       >= 0.8   && < 0.9,
-                       QuickCheck             >= 2.8   && < 2.9,
+                       QuickCheck             >= 2.8   && < 2.8.3,
                        quickcheck-instances   >= 0.3.6 && < 0.4