--- a/aeson.cabal
+++ b/aeson.cabal
@@ -82,6 +82,10 @@ flag th
   description: build TH bits
   default: True
 
+flag threaded
+  description: build threaded
+  default: True
+
 library
   default-language: Haskell2010
   hs-source-dirs: .
@@ -174,6 +178,10 @@ library
     hs-source-dirs: ffi
     other-modules: Data.Aeson.Parser.UnescapeFFI
 
+  if flag(threaded)
+    ghc-options: -threaded
+
+
 test-suite tests
   default-language: Haskell2010
   type: exitcode-stdio-1.0