diff --git a/.travis.yml b/.travis.yml
index 77ccea41b..6e7e78b15 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -14,6 +14,9 @@ env:
   - TMUX_VERSION=2.0
   - TMUX_VERSION=1.8
   - TMUX_VERSION=1.9a
+matrix:
+  allow_failures:
+  - env: TMUX_VERSION=master
 before_install:
   - export PIP_USE_MIRRORS=true
   - pip install --upgrade pytest  # https://github.com/travis-ci/travis-ci/issues/4873
diff --git a/CHANGES b/CHANGES
index dfcb03a32..987653e6e 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4,6 +4,10 @@ Changelog
 
 Here you can find the recent changes to libtmux
 
+- :release:`0.6.0 <2016-09-16>`
+- :bug:`-` Remove unused ``target_sesssion`` param in
+  ``Server.attach_session`` and ``Server.switch_client``.
+
 - :release:`0.5.1 <2016-08-18>`
 - :bug:`12` - fix logger message when tmux doesn't exist in ``PATH``
 
diff --git a/libtmux/common.py b/libtmux/common.py
index 614aecda1..e9b4416f2 100644
--- a/libtmux/common.py
+++ b/libtmux/common.py
@@ -420,3 +420,24 @@ def has_required_tmux_version(version=None):
             ' has %s installed. Upgrade your tmux to use libtmux.' % version
         )
     return version
+
+
+def session_check_name(session_name):
+    """Raises exception session name invalid, modeled after tmux function.
+
+    tmux(1) session names may not be empty, or include periods or colons.
+    These delimiters are reserved for noting session, window and pane.
+
+    :param session_name: name of session
+    :type session_name: string
+    :returns: void
+    :raises: :exc:`exc.BadSessionName`
+    """
+    if not session_name or len(session_name) == 0:
+        raise exc.BadSessionName("tmux session names may not be empty.")
+    elif '.' in session_name:
+        raise exc.BadSessionName(
+            "tmux session name \"%s\" may not contain periods.", session_name)
+    elif ':' in session_name:
+        raise exc.BadSessionName(
+            "tmux session name \"%s\" may not contain colons.", session_name)
diff --git a/libtmux/exc.py b/libtmux/exc.py
index 9187cfc79..155dd113b 100644
--- a/libtmux/exc.py
+++ b/libtmux/exc.py
@@ -20,6 +20,13 @@ class TmuxSessionExists(LibTmuxException):
     pass
 
 
+class BadSessionName(LibTmuxException):
+
+    """Session name is not allowed."""
+
+    pass
+
+
 class UnknownOption(LibTmuxException):
 
     """Option unknown to tmux show-option(s) or show-window-option(s)."""
diff --git a/libtmux/server.py b/libtmux/server.py
index 48da224f3..5439423a9 100644
--- a/libtmux/server.py
+++ b/libtmux/server.py
@@ -11,7 +11,8 @@
 import os
 
 from . import exc, formats
-from .common import EnvironmentMixin, TmuxRelationalObject, tmux_cmd
+from .common import EnvironmentMixin, TmuxRelationalObject, tmux_cmd, \
+    session_check_name
 from .session import Session
 
 logger = logging.getLogger(__name__)
@@ -318,10 +319,13 @@ def has_session(self, target_session):
         """Return True if session exists. ``$ tmux has-session``.
 
         :param: target_session: str of session name.
+        :raises: :exc:`exc.BadSessionName`
         :rtype: bool
 
         """
 
+        session_check_name(target_session)
+
         proc = self.cmd('has-session', '-t%s' % target_session)
 
         if not proc.stdout:
@@ -335,6 +339,8 @@ def has_session(self, target_session):
             return False
         elif 'can\'t find session' in proc.stdout:  # tmux 2.1
             return False
+        elif 'bad session name' in proc.stdout:  # tmux >= 1.9
+            return False
         elif 'session not found' in proc.stdout:
             return False
         else:
@@ -349,10 +355,12 @@ def kill_session(self, target_session=None):
 
         :param: target_session: str. note this accepts ``fnmatch(3)``. 'asdf'
             will kill 'asdfasd'.
-
+        :raises: :exc:`exc.BadSessionName`
         :rtype: :class:`Server`
 
         """
+        session_check_name(target_session)
+
         proc = self.cmd('kill-session', '-t%s' % target_session)
 
         if proc.stderr:
@@ -364,8 +372,9 @@ def switch_client(self, target_session):
         """``$ tmux switch-client``.
 
         :param: target_session: str. name of the session. fnmatch(3) works.
-
+        :raises: :exc:`exc.BadSessionName`
         """
+        session_check_name(target_session)
 
         proc = self.cmd('switch-client', '-t%s' % target_session)
 
@@ -376,8 +385,10 @@ def attach_session(self, target_session=None):
         """``$ tmux attach-session`` aka alias: ``$ tmux attach``.
 
         :param: target_session: str. name of the session. fnmatch(3) works.
-
+        :raises: :exc:`exc.BadSessionName`
         """
+        session_check_name(target_session)
+
         tmux_args = tuple()
         if target_session:
             tmux_args += ('-t%s' % target_session,)
@@ -418,9 +429,11 @@ def new_session(self,
         :param kill_session: Kill current session if ``$ tmux has-session``
                              Useful for testing workspaces.
         :type kill_session: bool
+        :raises: :exc:`exc.BadSessionName`
         :rtype: :class:`Session`
 
         """
+        session_check_name(session_name)
 
         if self.has_session(session_name):
             if kill_session:
diff --git a/libtmux/session.py b/libtmux/session.py
index 581ab26df..5689b65ed 100644
--- a/libtmux/session.py
+++ b/libtmux/session.py
@@ -11,7 +11,8 @@
 import os
 
 from . import exc, formats
-from .common import EnvironmentMixin, TmuxMappingObject, TmuxRelationalObject
+from .common import EnvironmentMixin, TmuxMappingObject, \
+    TmuxRelationalObject, session_check_name
 from .window import Window
 
 logger = logging.getLogger(__name__)
@@ -75,12 +76,8 @@ def cmd(self, *args, **kwargs):
             kwargs['-t'] = self.id
         return self.server.cmd(*args, **kwargs)
 
-    def attach_session(self, target_session=None):
-        """Return ``$ tmux attach-session`` aka alias: ``$ tmux attach``.
-
-        :param: target_session: str. name of the session. fnmatch(3) works.
-
-        """
+    def attach_session(self):
+        """Return ``$ tmux attach-session`` aka alias: ``$ tmux attach``."""
         proc = self.cmd('attach-session', '-t%s' % self.id)
 
         if proc.stderr:
@@ -94,10 +91,11 @@ def kill_session(self):
         if proc.stderr:
             raise exc.LibTmuxException(proc.stderr)
 
-    def switch_client(self, target_session=None):
+    def switch_client(self):
         """``$ tmux switch-client``.
 
         :param: target_session: str. note this accepts fnmatch(3).
+        :raises: :exc:`exc.LibTmuxException`
         """
         proc = self.cmd('switch-client', '-t%s' % self.id)
 
@@ -107,11 +105,14 @@ def switch_client(self, target_session=None):
     def rename_session(self, new_name):
         """Rename session and return new :class:`Session` object.
 
-        :param rename_session: new session name
-        :type rename_session: string
+        :param new_name: new session name
+        :type new_name: string
+        :raises: :exc:`exc.BadSessionName`
         :rtype: :class:`Session`
 
         """
+        session_check_name(new_name)
+
         proc = self.cmd(
             'rename-session',
             '-t%s' % self.id,
diff --git a/tests/test_common.py b/tests/test_common.py
index e519f1b19..79b443ca7 100644
--- a/tests/test_common.py
+++ b/tests/test_common.py
@@ -5,8 +5,8 @@
 
 import pytest
 
-from libtmux.common import has_required_tmux_version, which
-from libtmux.exc import LibTmuxException
+from libtmux.common import has_required_tmux_version, which, session_check_name
+from libtmux.exc import LibTmuxException, BadSessionName
 
 version_regex = re.compile(r'[0-9]\.[0-9]')
 
@@ -50,3 +50,20 @@ def test_which_no_tmuxp_found(monkeypatch):
     monkeypatch.setenv("PATH", "/")
     which('tmuxp')
     which('tmuxp', '/')
+
+
+@pytest.mark.parametrize("session_name,raises,exc_msg_regex", [
+    ('', True, 'may not be empty'),
+    (None, True, 'may not be empty'),
+    ("my great session.", True, 'may not contain periods'),
+    ("name: great session", True, 'may not contain colons'),
+    ("new great session", False, None),
+    ("ajf8a3fa83fads,,,a", False, None),
+])
+def test_session_check_name(session_name, raises, exc_msg_regex):
+    if raises:
+        with pytest.raises(BadSessionName) as exc_info:
+            session_check_name(session_name)
+        assert exc_info.match(exc_msg_regex)
+    else:
+        session_check_name(session_name)
diff --git a/tests/test_session.py b/tests/test_session.py
index d8356221b..0fe018d41 100644
--- a/tests/test_session.py
+++ b/tests/test_session.py
@@ -184,3 +184,34 @@ def test_unset_environment(session):
     assert session.show_environment('BAM') == 'OK'
     session.unset_environment('BAM')
     assert session.show_environment('BAM') is None
+
+
+@pytest.mark.parametrize("session_name,raises", [
+    ('hey.period', True),
+    ('hey:its a colon', True),
+    ('hey moo', False),
+])
+def test_periods_raise_badsessionname(server, session, session_name, raises):
+    new_name = session_name + 'moo'  # used for rename / switch
+    if raises:
+        with pytest.raises(exc.BadSessionName):
+            session.rename_session(new_name)
+
+        with pytest.raises(exc.BadSessionName):
+            server.new_session(session_name)
+
+        with pytest.raises(exc.BadSessionName):
+            server.has_session(session_name)
+
+        with pytest.raises(exc.BadSessionName):
+            server.switch_client(new_name)
+
+        with pytest.raises(exc.BadSessionName):
+            server.attach_session(new_name)
+
+    else:
+        server.new_session(session_name)
+        server.has_session(session_name)
+        session.rename_session(new_name)
+        with pytest.raises(exc.LibTmuxException):
+            server.switch_client(new_name)