diff --git a/demos/unit_test/wscript b/demos/unit_test/wscript
index 037a7624..bfbad807 100644
--- a/demos/unit_test/wscript
+++ b/demos/unit_test/wscript
@@ -16,7 +16,6 @@ out = 'build'
 def options(opt):
 	opt.load('compiler_cxx')
 	opt.load('waf_unit_test')
-	opt.add_option('--onlytests', action='store_true', default=True, help='Exec unit tests only', dest='only_tests')
 
 def configure(conf):
 	conf.load('compiler_cxx')
@@ -57,6 +56,7 @@ def build(bld):
 	# $ waf --alltests
 	# to set this behaviour permanenly:
 	bld.options.all_tests = True
+	#bld.options.clear_failed_tests = True
 
 	# debugging zone:
 	# $ waf --zones=ut
diff --git a/waflib/Tools/waf_unit_test.py b/waflib/Tools/waf_unit_test.py
index 27cd9a40..f5cbcfc5 100644
--- a/waflib/Tools/waf_unit_test.py
+++ b/waflib/Tools/waf_unit_test.py
@@ -132,13 +132,18 @@ class utest(Task.Task):
 		proc = Utils.subprocess.Popen(self.ut_exec, cwd=cwd, env=self.get_test_env(), stderr=Utils.subprocess.PIPE, stdout=Utils.subprocess.PIPE)
 		(stdout, stderr) = proc.communicate()
 
-		tup = (filename, proc.returncode, stdout, stderr)
+		self.waf_unit_test_results = tup = (filename, proc.returncode, stdout, stderr)
 		testlock.acquire()
 		try:
 			return self.generator.add_test_results(tup)
 		finally:
 			testlock.release()
 
+	def post_run(self):
+		super(utest, self).post_run()
+		if getattr(Options.options, 'clear_failed_tests', False) and self.waf_unit_test_results[1]:
+			self.generator.bld.task_sigs[self.uid()] = None
+
 def summary(bld):
 	"""
 	Display an execution summary::
@@ -194,6 +199,7 @@ def options(opt):
 	"""
 	opt.add_option('--notests', action='store_true', default=False, help='Exec no unit tests', dest='no_tests')
 	opt.add_option('--alltests', action='store_true', default=False, help='Exec all unit tests', dest='all_tests')
+	opt.add_option('--clear-failed', action='store_true', default=False, help='Force failed unit tests to run again next time', dest='clear_failed_tests')
 	opt.add_option('--testcmd', action='store', default=False,
 	 help = 'Run the unit tests using the test-cmd string'
 	 ' example "--test-cmd="valgrind --error-exitcode=1'