diff --git a/utils/haddock/haddock.cabal b/utils/haddock/haddock.cabal
index 51922913a4add12c2134e2daf38c2607df20e486..32d104f54f8fb0d0f783bfabc1fad1d13b4aa452 100644
--- a/utils/haddock/haddock.cabal
+++ b/utils/haddock/haddock.cabal
@@ -60,11 +60,18 @@ flag in-ghc-tree
   default: False
   manual: True
 
+flag threaded
+  description: Build haddock with the threaded RTS
+  default: True
+  manual: True
+
 executable haddock
   default-language:     Haskell2010
   main-is:              Main.hs
   hs-source-dirs:       driver
-  ghc-options:          -funbox-strict-fields -Wall -Wincomplete-uni-patterns -Wincomplete-record-updates -O2 -threaded
+  ghc-options:          -funbox-strict-fields -Wall -Wincomplete-uni-patterns -Wincomplete-record-updates -O2
+  if flag(threaded)
+    ghc-options: -threaded
 
   -- haddock typically only supports a single GHC major version
   build-depends: