diff --git a/Lib/test/regrtest.py b/Lib/test/regrtest.py
index 183c12b..2c09f63 100755
--- a/Lib/test/regrtest.py
+++ b/Lib/test/regrtest.py
@@ -115,10 +115,11 @@
         elif o in ('-l', '--findleaks'):
             findleaks = 1
         elif o in ('-u', '--use'):
-            use_resources = [x.lower() for x in a.split(',')]
-            for r in use_resources:
+            u = [x.lower() for x in a.split(',')]
+            for r in u:
                 if r not in ('largefile', 'network'):
                     usage(1, 'Invalid -u/--use option: %s' % a)
+            use_resources.extend(u)
     if generate and verbose:
         usage(2, "-g and -v don't go together!")
 
diff --git a/Lib/test/test_support.py b/Lib/test/test_support.py
index 8539997..5391f68 100644
--- a/Lib/test/test_support.py
+++ b/Lib/test/test_support.py
@@ -20,7 +20,7 @@
     """
 
 verbose = 1              # Flag set to 0 by regrtest.py
-use_resources = []       # Flag set to [] by regrtest.py
+use_resources = None       # Flag set to [] by regrtest.py
 
 def unload(name):
     try:
@@ -38,7 +38,7 @@
             pass
 
 def requires(resource, msg=None):
-    if resource not in use_resources:
+    if use_resources is not None and resource not in use_resources:
         if msg is None:
             msg = "Use of the `%s' resource not enabled" % resource
         raise TestSkipped(msg)