diff --git a/unix/syscall_darwin.1_13.go b/unix/syscall_darwin.1_13.go
index 24960c38..f911617b 100644
--- a/unix/syscall_darwin.1_13.go
+++ b/unix/syscall_darwin.1_13.go
@@ -27,8 +27,6 @@ func libc_fdopendir_trampoline()
 
 func Getdirentries(fd int, buf []byte, basep *uintptr) (n int, err error) {
 	// Simulate Getdirentries using fdopendir/readdir_r/closedir.
-	const ptrSize = unsafe.Sizeof(uintptr(0))
-
 	// We store the number of entries to skip in the seek
 	// offset of fd. See issue #31368.
 	// It's not the full required semantics, but should handle the case