diff --git a/LICENSE b/LICENSE
--- a/LICENSE
+++ b/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2016-2017 Moritz Schulte
+Copyright (c) 2016-2020 Moritz Clasmeier
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
diff --git a/partial-order.cabal b/partial-order.cabal
--- a/partial-order.cabal
+++ b/partial-order.cabal
@@ -1,5 +1,5 @@
 name:                partial-order
-version:             0.1.2.1
+version:             0.2.0.0
 synopsis:            Provides typeclass suitable for types admitting a partial order
 description:         This packages provides the PartialOrd typeclass suitable for
                      types admitting a partial order.
@@ -13,34 +13,49 @@
 homepage:            https://github.com/mtesseract/haskell-partial-order
 license:             BSD3
 license-file:        LICENSE
-author:              Moritz Schulte
+author:              Moritz Clasmeier
 maintainer:          mtesseract@silverratio.net
-copyright:           (c) 2016-2017 Moritz Schulte
+copyright:           (c) 2016-2020 Moritz Clasmeier
 category:            Data
 build-type:          Simple
 -- extra-source-files:
 cabal-version:       >=1.10
 
+flag extra-instances
+  description:
+    Include additional instances of PartialOrd in Data.Set
+
 library
   hs-source-dirs:      src
   exposed-modules:     Data.PartialOrd
   build-depends:       base >= 4.7 && < 5
-                     , containers >= 0.5.0.0 && < 0.6
   default-language:    Haskell2010
 
+  default-extensions:  CPP
+
+  if flag(extra-instances)
+    build-depends:     containers >= 0.5.0.0 && < 0.7
+    CPP-Options:       -DEXTRA_INSTANCES
+
 test-suite partial-order-test
   type:                exitcode-stdio-1.0
   hs-source-dirs:      test
   main-is:             Spec.hs
   build-depends:       base
                      , partial-order
-                     , HUnit >= 1.5.0.0 && < 1.6
+                     , HUnit >= 1.5.0.0 && < 1.7
                      , test-framework >= 0.8.1.1 && < 0.9
                      , test-framework-hunit >= 0.3.0.2 && < 0.4
                      , test-framework-quickcheck2 >= 0.3.0.3 && < 0.4
-                     , containers >= 0.5.0.0 && < 0.6
+                     , containers >= 0.5.0.0 && < 0.7
   ghc-options:         -threaded -rtsopts -with-rtsopts=-N
   default-language:    Haskell2010
+
+  default-extensions:  CPP
+
+  if flag(extra-instances)
+    build-depends:     containers >= 0.5.0.0 && < 0.7
+    CPP-Options:       -DEXTRA_INSTANCES
 
 source-repository head
   type:     git
diff --git a/src/Data/PartialOrd.hs b/src/Data/PartialOrd.hs
--- a/src/Data/PartialOrd.hs
+++ b/src/Data/PartialOrd.hs
@@ -30,7 +30,9 @@
 import qualified Data.Ord as Ord
 import qualified Data.Eq as Eq
 import qualified Data.List as List
+#if EXTRA_INSTANCES
 import qualified Data.Set as Set
+#endif
 import qualified Data.Foldable as Foldable
 
 class PartialOrd a where
@@ -82,9 +84,11 @@
 instance PartialOrd Float where
   (<=) = (Ord.<=)
 
+#if EXTRA_INSTANCES
 -- | Define the partial order in terms of the subset relation.
 instance (Ord.Ord a) => PartialOrd (Set.Set a) where
   (<=) = Set.isSubsetOf
+#endif
 
 -- | Define the partial order in terms of the sublist relation.
 instance PartialOrd a => PartialOrd [a] where
diff --git a/test/Spec.hs b/test/Spec.hs
--- a/test/Spec.hs
+++ b/test/Spec.hs
@@ -5,7 +5,9 @@
 import Test.Framework.Providers.QuickCheck2 (testProperty)
 import Data.List
 import Data.Ord
+#if EXTRA_INSTANCES
 import qualified Data.Set as S
+#endif
 import qualified Data.PartialOrd as PO
 import Test.HUnit ((@?=))
 
@@ -56,6 +58,7 @@
     , testProperty "antisymmetry"
       (\ a b -> prop_antisymmetry (a :: [Int]) (b :: [Int]))
     ]
+#if EXTRA_INSTANCES
   , testGroup "Set Properties"
     [
       testProperty "=="
@@ -83,7 +86,7 @@
     , testProperty "antisymmetry"
       (\ a b -> prop_antisymmetry (a :: S.Set Int) (b :: S.Set Int))
     ]
-
+#endif
   , testGroup "Maxima & Minima"
     [
       testProperty "maxima exist"