diff --git a/unittests/runtests.py b/unittests/runtests.py
index c7f0b01d..9009389d 100755
--- a/unittests/runtests.py
+++ b/unittests/runtests.py
@@ -89,6 +89,7 @@ class MyTestSuite(unittest.TestSuite):
             #    output = output.decode('ascii') 
             output = output.rstrip()
             rval = sp.wait()
+            sp.stdout.close()
             if rval:
                 print("Command '%s' failed with exit code %d." % (cmd, rval))
                 sys.exit(rval)