diff --git a/simplexmq.cabal b/simplexmq.cabal
index 4a16a969c..e5f49232f 100644
--- a/simplexmq.cabal
+++ b/simplexmq.cabal
@@ -136,7 +136,7 @@ library
     , x509-store ==1.6.*
     , x509-validation ==1.6.*
   if flag(swift)
-    ghc-options: -DswiftJSON
+    cpp-options: -DswiftJSON
   default-language: Haskell2010
 
 executable ntf-server