diff --git a/CHANGES.md b/CHANGES.md
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,7 @@
+### Version 0.6.2 (2019-04-26)
+  
+  * Define `MonadFail Ok`.
+
 ### Version 0.6.1 (2019-03-04)
 
   * Escape double '??' to a literal '?
diff --git a/postgresql-simple.cabal b/postgresql-simple.cabal
--- a/postgresql-simple.cabal
+++ b/postgresql-simple.cabal
@@ -1,6 +1,6 @@
 Cabal-version:       1.12
 Name:                postgresql-simple
-Version:             0.6.1
+Version:             0.6.2
 
 Synopsis:            Mid-Level PostgreSQL client library
 Description:
@@ -28,7 +28,8 @@
    || == 8.0.2
    || == 8.2.2
    || == 8.4.4
-   || == 8.6.3
+   || == 8.6.5
+   || == 8.8.1
 
 Library
   default-language: Haskell2010
@@ -97,7 +98,8 @@
 
   if !impl(ghc >= 8.0)
     Build-depends:
-      semigroups >=0.18.5 && <0.19
+      fail       >=4.9.0.0 && <4.10,
+      semigroups >=0.18.5  && <0.19
 
   if !impl(ghc >= 7.6)
     Build-depends:
diff --git a/src/Database/PostgreSQL/Simple/Ok.hs b/src/Database/PostgreSQL/Simple/Ok.hs
--- a/src/Database/PostgreSQL/Simple/Ok.hs
+++ b/src/Database/PostgreSQL/Simple/Ok.hs
@@ -37,6 +37,8 @@
 import Control.Monad(MonadPlus(..))
 import Data.Typeable
 
+import qualified Control.Monad.Fail as Fail
+
 -- FIXME:   [SomeException] should probably be something else,  maybe
 --          a difference list (or a tree?)
 
@@ -77,6 +79,11 @@
     Errors es >>= _ = Errors es
     Ok a      >>= f = f a
 
+#if !(MIN_VERSION_base(4,13,0))
+    fail = Fail.fail
+#endif
+
+instance Fail.MonadFail Ok where
     fail str = Errors [SomeException (ErrorCall str)]
 
 -- | a way to reify a list of exceptions into a single exception