diff --git a/src/sys/unix/size.rs b/src/sys/unix/size.rs
index 9979280..17f2515 100644
--- a/src/sys/unix/size.rs
+++ b/src/sys/unix/size.rs
@@ -14,7 +14,7 @@ struct TermSize {
 pub fn terminal_size() -> io::Result<(u16, u16)> {
     unsafe {
         let mut size: TermSize = mem::zeroed();
-        cvt(ioctl(STDOUT_FILENO, TIOCGWINSZ, &mut size as *mut _))?;
+        cvt(ioctl(STDOUT_FILENO, TIOCGWINSZ.into(), &mut size as *mut _))?;
         Ok((size.col as u16, size.row as u16))
     }
 }