diff --git a/bitbake/lib/bb/ui/knotty.py b/bitbake/lib/bb/ui/knotty.py
index 3784c93ad8..41a943adf8 100644
--- a/bitbake/lib/bb/ui/knotty.py
+++ b/bitbake/lib/bb/ui/knotty.py
@@ -131,7 +131,7 @@ class TerminalFilter(object):
     def getTerminalColumns(self):
         def ioctl_GWINSZ(fd):
             try:
-                cr = struct.unpack('hh', fcntl.ioctl(fd, self.termios.TIOCGWINSZ, '1234'))
+                cr = struct.unpack('hhhh', fcntl.ioctl(fd, self.termios.TIOCGWINSZ, b'12345678'))[0:2]
             except:
                 return None
             return cr