diff --git a/platform/posix/src/System/Terminal/Platform.hsc b/platform/posix/src/System/Terminal/Platform.hsc
index 7846334..46ca5fb 100644
--- a/platform/posix/src/System/Terminal/Platform.hsc
+++ b/platform/posix/src/System/Terminal/Platform.hsc
@@ -302,8 +302,8 @@ foreign import ccall unsafe "tcgetattr"
 foreign import ccall unsafe "tcsetattr"
   unsafeSetTermios :: CInt -> CInt -> Ptr Termios -> IO CInt
 
-foreign import ccall unsafe "ioctl"
-  unsafeIOCtl :: CInt -> CInt -> Ptr a -> IO CInt
+foreign import capi unsafe "ioctl"
+  unsafeIOCtl :: CInt -> CULong -> Ptr a -> IO CInt
 
 foreign import ccall unsafe
   stg_sig_install :: CInt -> CInt -> Ptr a -> IO CInt