diff --git a/common/conf_check.py b/common/conf_check.py
index d81d9f30c5bc864f45f7fa4be21f37b4b6110c11..785c8a66f12228392b4a10e8dc7e68db0b8dcf18 100644
--- a/common/conf_check.py
+++ b/common/conf_check.py
@@ -35,6 +35,7 @@ class ConfCheck:
         devnull = open("/dev/null", "w")
         ret = subprocess.Popen(shlex('test -e ' + file), stdout = devnull, stderr = devnull)
         ret.communicate()
+        devnull.close()
         if 0 == ret.returncode:
             return True
         else: