diff --git a/basis/unix/ffi/macosx/macosx.factor b/basis/unix/ffi/macosx/macosx.factor
index 6e994fbe82..5a04ebe98c 100644
--- a/basis/unix/ffi/macosx/macosx.factor
+++ b/basis/unix/ffi/macosx/macosx.factor
@@ -266,9 +266,9 @@ CONSTANT: SIGUSR1   30
 CONSTANT: SIGUSR2   31
 
 STRUCT: sf_hdtr
-    { headers iovec* }
+    { headers void* }
     { hdr_cnt int }
-    { trailers iovec* }
+    { trailers void* }
     { trl_cnt int } ;
 
 FUNCTION: int sendfile ( int fd, int s, off_t offset, off_t* len, sf_hdtr* hdtr, int flags ) ;