diff --git a/avocado/utils/filelock.py b/avocado/utils/filelock.py
index ac46084556eacd13c0e1dcad64c0201d57456fc2..b996f6e0807ab9512382faef9dc6e551c1cf8547 100644
--- a/avocado/utils/filelock.py
+++ b/avocado/utils/filelock.py
@@ -42,7 +42,7 @@ class FileLock(object):
 
     def __init__(self, filename, timeout=0):
         self.filename = '%s.lock' % filename
-        self.pid = b'%r' % os.getpid()
+        self.pid = '{0}'.format(os.getpid()).encode()
         self.locked = False
         self.timeout = timeout