diff --git a/gunicorn/util.py b/gunicorn/util.py
index 75224f82..9850c773 100644
--- a/gunicorn/util.py
+++ b/gunicorn/util.py
@@ -101,8 +101,9 @@ def get_maxfd():
     return maxfd
 
 def close_on_exec(fd):
-    flags = fcntl.fcntl(fd, fcntl.F_GETFD) | fcntl.FD_CLOEXEC
-    fcntl.fcntl(fd, fcntl.F_SETFL, flags)
+    flags = fcntl.fcntl(fd, fcntl.F_GETFD)
+    flags |= fcntl.FD_CLOEXEC
+    fcntl.fcntl(fd, fcntl.F_SETFD, flags)
     
 def set_non_blocking(fd):
     flags = fcntl.fcntl(fd, fcntl.F_GETFL) | os.O_NONBLOCK