diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,13 @@
 # Changelog for `password`
 
+## 3.1.0.0
+
+-   Switched default cryptographic backend library from `cryptonite` to `crypton`.
+    The `crypton` flag is now a no-op, and the `cryptonite` flag is needed to build
+    the `password` library using the `cryptonite` library.
+    Thanks to [@Vlix](https://github.com/Vlix)
+    [#81](https://github.com/cdepillabout/password/pull/81)
+
 ## 3.0.4.0
 
 -   Support `base64` package up to and including `base64-1.0`.
diff --git a/password.cabal b/password.cabal
--- a/password.cabal
+++ b/password.cabal
@@ -1,7 +1,7 @@
 cabal-version: 1.12
 
 name:           password
-version:        3.0.4.0
+version:        3.1.0.0
 category:       Data
 synopsis:       Hashing and checking of passwords
 description:
@@ -58,13 +58,13 @@
 
 flag crypton
   description: Use the [crypton] library as the cryptographic backend.
+    (Does nothing since version 3.1.0.0; might be removed in a future major version)
   default: False
   manual: True
 
 flag cryptonite
   description:
     Use the [cryptonite] library as the cryptographic backend.
-    (Does nothing until a future major version)
   default: False
   manual: True
 
@@ -120,15 +120,12 @@
       -Wall
   default-language:
       Haskell2010
-  -- At some future major version bump, this should
-  -- be changed to the [cryptonite] flag and that
-  -- `if flag(cryptonite) build-depends: cryptonite`
-  if flag(crypton)
+  if flag(cryptonite)
     build-depends:
-      crypton     >= 0.31   && < 0.35
+      cryptonite  >= 0.15.1   && < 0.31
   else
     build-depends:
-      cryptonite  >= 0.15.1   && < 0.31
+      crypton     >= 0.31   && < 1.1
 
 test-suite doctests
   type:
@@ -143,10 +140,8 @@
       base >=4.9 && <5
     , base-compat
     , doctest
-    , password
     , QuickCheck
     , quickcheck-instances
-    , template-haskell
   default-language:
       Haskell2010
 
@@ -195,7 +190,6 @@
     , bytestring
     , memory
     , quickcheck-instances
-    , scrypt
     , tasty
     , tasty-hunit
     , tasty-quickcheck
@@ -203,6 +197,12 @@
     , text
   default-language:
       Haskell2010
+
+  if os(darwin)
+    cpp-options: -DIS_MAC_OS
+  else
+    build-depends: scrypt
+
   if flag(argon2)
     cpp-options:
       -DCABAL_FLAG_argon2
@@ -215,12 +215,9 @@
   if flag(scrypt)
     cpp-options:
       -DCABAL_FLAG_scrypt
-  -- At some future major version bump, this should
-  -- be changed to the [cryptonite] flag and that
-  -- `if flag(cryptonite) build-depends: cryptonite`
-  if flag(crypton)
+  if flag(cryptonite)
     build-depends:
-      crypton
+      cryptonite
   else
     build-depends:
-      cryptonite
+      crypton
diff --git a/src/Data/Password/Bcrypt.hs b/src/Data/Password/Bcrypt.hs
--- a/src/Data/Password/Bcrypt.hs
+++ b/src/Data/Password/Bcrypt.hs
@@ -221,8 +221,11 @@
 extractParams :: PasswordHash Bcrypt -> Maybe Int
 extractParams (PasswordHash passHash) =
   case T.split (== '$') passHash of
-    [_, version, cost, _pass] -> do
-      guard $ elem version $ map T.pack ["2", "2a", "2x", "2y", "2b"]
+    [prefix, version, cost, _pass] -> do
+      guard $
+        -- 'prefix' should be nothing, because the hash should start with a '$'
+        -- The order of versions is based on most likely to encounter in the wild.
+        T.null prefix && elem version (T.pack <$> ["2b", "2y", "2x", "2a", "2"])
       readMaybe $ T.unpack cost
     _ -> Nothing
 
diff --git a/src/Data/Password/Validate.hs b/src/Data/Password/Validate.hs
--- a/src/Data/Password/Validate.hs
+++ b/src/Data/Password/Validate.hs
@@ -202,8 +202,9 @@
 
 import Data.Char (chr, isAsciiLower, isAsciiUpper, isDigit, ord)
 import Data.Function (on)
-import Data.List (foldl')
-
+#if !MIN_VERSION_base(4,20,0)
+import Data.Foldable (foldl')
+#endif
 import Data.Text (Text)
 import qualified Data.Text as T
 import Language.Haskell.TH (Exp, Q, appE)
diff --git a/test/tasty/Scrypt.hs b/test/tasty/Scrypt.hs
--- a/test/tasty/Scrypt.hs
+++ b/test/tasty/Scrypt.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 module Scrypt where
 
 import Data.Maybe (fromJust)
@@ -7,7 +8,9 @@
 import Test.Tasty.QuickCheck
 import Test.QuickCheck.Instances.Text ()
 
+#ifndef IS_MAC_OS
 import qualified Crypto.Scrypt as Scrypt
+#endif
 import Data.Password.Types
 import Data.Password.Scrypt
 
@@ -24,7 +27,9 @@
                  checkPassword
                  extractParams
                  testsParams8Rounds
+#ifndef IS_MAC_OS
   , testProperty "scrypt <-> cryptonite" $ withMaxSuccess 10 checkScrypt
+#endif
   ]
   where
     hash8Rounds = hashPasswordWithParams testsParams8Rounds
@@ -32,6 +37,7 @@
     hash4Rounds = hashPasswordWithParams testsParams4Rounds
     testsParams4Rounds = defaultParams{ scryptRounds = 4, scryptSalt = 16 }
 
+#ifndef IS_MAC_OS
 checkScrypt :: Text -> Property
 checkScrypt pass = ioProperty $ do
   s@(Scrypt.Salt salt) <- Scrypt.newSalt
@@ -41,3 +47,4 @@
       PasswordHash ourHash =
         hashPasswordWithSalt defaultParams{ scryptRounds = 8 } (Salt salt) $ mkPassword pass
   return $ scryptHash === encodeUtf8 ourHash
+#endif