diff --git a/_pytest/config.py b/_pytest/config.py
index ce7468f72..14ed4d09b 100644
--- a/_pytest/config.py
+++ b/_pytest/config.py
@@ -990,11 +990,15 @@ class Config(object):
 
     def _initini(self, args):
         ns, unknown_args = self._parser.parse_known_and_unknown_args(args, namespace=self.option.copy())
-        r = determine_setup(ns.inifilename, ns.file_or_dir + unknown_args, warnfunc=self.warn)
+        rootdir = ns.rootdir if ns.rootdir else None
+        r = determine_setup(ns.inifilename, ns.file_or_dir + unknown_args, warnfunc=self.warn, rootdir_cmd_arg=rootdir)
         self.rootdir, self.inifile, self.inicfg = r
         self._parser.extra_info['rootdir'] = self.rootdir
         self._parser.extra_info['inifile'] = self.inifile
         self.invocation_dir = py.path.local()
+        if ns.rootdir:
+            self.invocation_dir = self.rootdir
+            sys.path.append(str(self.rootdir))
         self._parser.addini('addopts', 'extra command line options', 'args')
         self._parser.addini('minversion', 'minimally required pytest version')
         self._override_ini = ns.override_ini or ()
@@ -1323,7 +1327,7 @@ def get_dirs_from_args(args):
     ]
 
 
-def determine_setup(inifile, args, warnfunc=None):
+def determine_setup(inifile, args, warnfunc=None, rootdir_cmd_arg=None):
     dirs = get_dirs_from_args(args)
     if inifile:
         iniconfig = py.iniconfig.IniConfig(inifile)
@@ -1346,6 +1350,11 @@ def determine_setup(inifile, args, warnfunc=None):
                     is_fs_root = os.path.splitdrive(str(rootdir))[1] == '/'
                     if is_fs_root:
                         rootdir = ancestor
+    if rootdir_cmd_arg:
+        rootdir_abs_path = py.path.local(rootdir_cmd_arg)
+        if not os.path.isdir(str(rootdir_abs_path)):
+            raise UsageError("Directory '{}' not found. Check your '--rootdir' option.".format(rootdir_abs_path))
+        rootdir = rootdir_abs_path
     return rootdir, inifile, inicfg or {}
 
 
diff --git a/_pytest/main.py b/_pytest/main.py
index 7fa86db17..ed70bfb31 100644
--- a/_pytest/main.py
+++ b/_pytest/main.py
@@ -33,9 +33,6 @@ def pytest_addoption(parser):
     parser.addini("testpaths", "directories to search for tests when no files or directories are given in the "
                                "command line.",
                   type="args", default=[])
-    parser.addini("rootdir", "define root directory for tests. If this parameter defined command argument "
-                  "'--rootdir' will not work",
-                  type="args", default=[])
     # parser.addini("dirpatterns",
     #    "patterns specifying possible locations of test files",
     #    type="linelist", default=["**/test_*.txt",
@@ -60,7 +57,7 @@ def pytest_addoption(parser):
                      dest="rootdir",
                      help="Define root directory for tests. Can be relative path: 'root_dir', './root_dir', "
                           "'root_dir/another_dir/'; absolute path: '/home/user/root_dir'; path with variables: "
-                          "'$HOME/root_dir'. If parameter 'rootdir' defined in *.ini file this argument will not work")
+                          "'$HOME/root_dir'.")
 
     group = parser.getgroup("collect", "collection")
     group.addoption('--collectonly', '--collect-only', action="store_true",
@@ -292,16 +289,6 @@ class Session(nodes.FSCollector):
         self._norecursepatterns = config.getini("norecursedirs")
         self.startdir = py.path.local()
 
-        rootdir_ini = config.getini('rootdir')
-        self.rootdir = rootdir_ini[0] if rootdir_ini else config.option.rootdir
-        if self.rootdir:
-            rootdir_abs_path = py.path.local(self.rootdir)
-            if not os.path.isdir(str(rootdir_abs_path)):
-                raise UsageError("Directory '{}' not found. Check your '--rootdir' option.".format(rootdir_abs_path))
-            config.invocation_dir = rootdir_abs_path
-            config.rootdir = rootdir_abs_path
-            sys.path.append(str(rootdir_abs_path))
-
         self.config.pluginmanager.register(self, name="session")
 
     def _makeid(self):
diff --git a/testing/test_session.py b/testing/test_session.py
index 732a3af06..5c1b9918f 100644
--- a/testing/test_session.py
+++ b/testing/test_session.py
@@ -266,21 +266,3 @@ def test_rootdir_option_arg(testdir):
 
     result = testdir.runpytest("--rootdir=root")
     result.stdout.fnmatch_lines(["*1 passed*"])
-
-
-def test_rootdir_option_ini_file(testdir):
-    rootdir = testdir.mkdir("root")
-    rootdir.join("spoon.py").write("spoon_number = 1")
-    testsdir = rootdir.mkdir("tests")
-    testsdir.join("test_one.py").write("from spoon import spoon_number\ndef test_one():\n    assert spoon_number")
-
-    result = testdir.runpytest()
-    result.stdout.fnmatch_lines(["*No module named*spoon*"])
-    testdir.makeini("""
-            [pytest]
-            rootdir=root
-        """)
-    result = testdir.runpytest()
-    result.stdout.fnmatch_lines(["*1 passed*"])
-    result = testdir.runpytest("--rootdir=ignored_argument")
-    result.stdout.fnmatch_lines(["*1 passed*"])