diff --git a/tester.py b/tester.py
index 2725d146eb35f1c485e55ad3782d7497781339df..795c7612dc9c0d4f0aaa04eb23327988eeaf403c 100755
--- a/tester.py
+++ b/tester.py
@@ -40,7 +40,7 @@ def strip_colors(text):
 
 
 class Tester():
-    USAGE = '''%s [-e] [-f] [-b] [-d] [-h]
+    USAGE = '''%s [-e] [-f] [-b] [-d] [-h] [msuser]
     -e: send email with report.
     -f: send email with report only if at least one test failed.
     -b: run only basic tests (exclude mediaserver tests).
@@ -55,15 +55,23 @@ class Tester():
         log('\033[96m- UbiCast applications tester -\033[0m')
         log('\033[96m-------------------------------\033[0m')
         args = list(args)
+        msuser = None
         # Check if help is required
         if '-h' in args:
             log('USAGE: ' + self.USAGE)
             sys.exit(0)
-        for arg in args:
-            if arg not in self.VALID_ARGS:
+        for index, arg in enumerate(args):
+            if arg not in self.VALID_ARGS and index + 1 != len(args):
                 log('Invalid argument given: "%s".\n' % arg)
                 log('USAGE: ' + self.USAGE)
                 sys.exit(1)
+            else:
+                log("Optional target user : %s" % arg)
+                if not os.path.isdir(os.path.join('/home', arg)):
+                    log("Mediaserver user %s does not exist" % arg)
+                    sys.exit(1)
+                else:
+                    msuser = arg
         # Check current dir
         root_dir = utils.get_dir(__file__)
         if root_dir != '':
@@ -89,7 +97,7 @@ class Tester():
         email = '-e' in args
         email_if_fail = '-f' in args
         basic_only = '-b' in args
-        tests = self.discover_tests(basic_only)
+        tests = self.discover_tests(basic_only, msuser)
         if not tests:
             sys.exit(1)
         exit_code = self.run_tests(tests, email, email_if_fail)
@@ -123,7 +131,7 @@ class Tester():
             criticality = 'not specified'
         return criticality, description
 
-    def discover_tests(self, basic_only=False):
+    def discover_tests(self, basic_only=False, msuser=None):
         ignored_tests = utils.get_conf('TESTER_IGNORED_TESTS', '').split(',')
         # Get standard tests
         path = os.path.join(self.root_dir, 'tests')
@@ -151,10 +159,12 @@ class Tester():
         if basic_only:
             tests.sort(key=lambda i: (-criticalities_map.get(i[1], 0), i[0]))
             return tests
+        elif msuser:
+            tests = list()
         # Get MS instances
         ms_users = list()
         for user in os.listdir('/home'):
-            if os.path.exists('/home/%s/msinstance' % user):
+            if os.path.exists('/home/%s/msinstance' % user) and user == msuser:
                 ms_users.append(user)
         # Get MediaServer tests
         if ms_users: