diff --git a/poetry.lock b/poetry.lock
index 69ba5a51927..cddc79fb8c9 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -37,7 +37,7 @@ version = "1.4.4"
 [[package]]
 category = "dev"
 description = "Atomic file writes."
-marker = "python_version >= \"3\" and sys_platform == \"win32\" or python_version < \"3\""
+marker = "python_version >= \"3\" and sys_platform == \"win32\" or sys_platform == \"win32\" or python_version < \"3\""
 name = "atomicwrites"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
@@ -46,7 +46,6 @@ version = "1.4.0"
 [[package]]
 category = "dev"
 description = "Classes Without Boilerplate"
-marker = "python_version >= \"3.6\" and python_version < \"4.0\" or python_version >= \"3\" or python_version < \"3\""
 name = "attrs"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
@@ -61,7 +60,6 @@ tests = ["coverage", "hypothesis", "pympler", "pytest (>=4.3.0)", "six", "zope.i
 [[package]]
 category = "dev"
 description = "Internationalization utilities"
-marker = "python_version < \"3\" or python_version >= \"3\""
 name = "babel"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
@@ -90,18 +88,24 @@ marker = "python_version >= \"3.6\" and python_version < \"4.0\""
 name = "black"
 optional = false
 python-versions = ">=3.6"
-version = "19.10b0"
+version = "20.8b1"
 
 [package.dependencies]
 appdirs = "*"
-attrs = ">=18.1.0"
-click = ">=6.5"
+click = ">=7.1.2"
+mypy-extensions = ">=0.4.3"
 pathspec = ">=0.6,<1"
-regex = "*"
-toml = ">=0.9.4"
+regex = ">=2020.1.8"
+toml = ">=0.10.1"
 typed-ast = ">=1.4.0"
+typing-extensions = ">=3.7.4"
+
+[package.dependencies.dataclasses]
+python = "<3.7"
+version = ">=0.6"
 
 [package.extras]
+colorama = ["colorama (>=0.4.3)"]
 d = ["aiohttp (>=3.3.2)", "aiohttp-cors"]
 
 [[package]]
@@ -205,7 +209,7 @@ testing = ["pytest (>=3.5,<3.7.3 || >3.7.3)", "pytest-checkdocs (>=1.2)", "pytes
 [[package]]
 category = "dev"
 description = "Backports and enhancements for the contextlib module"
-marker = "python_version < \"3.4\""
+marker = "python_version < \"3.4\" or python_version >= \"3\" and python_version < \"3.4\""
 name = "contextlib2"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
@@ -243,6 +247,15 @@ pep8test = ["black", "flake8", "flake8-import-order", "pep8-naming"]
 ssh = ["bcrypt (>=3.1.5)"]
 test = ["pytest (>=3.6.0,<3.9.0 || >3.9.0,<3.9.1 || >3.9.1,<3.9.2 || >3.9.2)", "pretend", "iso8601", "pytz", "hypothesis (>=1.11.4,<3.79.2 || >3.79.2)"]
 
+[[package]]
+category = "dev"
+description = "A backport of the dataclasses module for Python 3.6"
+marker = "python_version >= \"3.6\" and python_version < \"3.7\""
+name = "dataclasses"
+optional = false
+python-versions = ">=3.6, <3.7"
+version = "0.7"
+
 [[package]]
 category = "dev"
 description = "Docutils -- Python Documentation Utilities"
@@ -340,7 +353,6 @@ version = "2.10"
 [[package]]
 category = "dev"
 description = "Getting image size from png/jpeg/jpeg2000/gif file"
-marker = "python_version < \"3\" or python_version >= \"3\""
 name = "imagesize"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
@@ -377,7 +389,6 @@ testing = ["packaging", "pep517", "importlib-resources (>=1.3)"]
 [[package]]
 category = "dev"
 description = "iniconfig: brain-dead simple config-ini parsing"
-marker = "python_version >= \"3\""
 name = "iniconfig"
 optional = false
 python-versions = "*"
@@ -436,7 +447,6 @@ dev = ["testpath"]
 [[package]]
 category = "dev"
 description = "A very fast and expressive template engine."
-marker = "python_version < \"3\" or python_version >= \"3\""
 name = "jinja2"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"
@@ -491,7 +501,6 @@ version = "0.8.3"
 [[package]]
 category = "dev"
 description = "Safely add untrusted strings to HTML/XML markup."
-marker = "python_version < \"3\" or python_version >= \"3\""
 name = "markupsafe"
 optional = false
 python-versions = ">=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*"
@@ -541,12 +550,20 @@ six = ">=1.0.0,<2.0.0"
 [[package]]
 category = "dev"
 description = "More routines for operating on iterables, beyond itertools"
-marker = "python_version >= \"3\""
 name = "more-itertools"
 optional = false
 python-versions = ">=3.5"
 version = "8.4.0"
 
+[[package]]
+category = "dev"
+description = "Experimental type system extensions for programs checked with the mypy typechecker."
+marker = "python_version >= \"3.6\" and python_version < \"4.0\""
+name = "mypy-extensions"
+optional = false
+python-versions = "*"
+version = "0.4.3"
+
 [[package]]
 category = "dev"
 description = "Core utilities for Python packages"
@@ -578,7 +595,7 @@ version = "*"
 [[package]]
 category = "dev"
 description = "Object-oriented filesystem paths"
-marker = "python_version >= \"3\" and python_version < \"3.6\""
+marker = "python_version >= \"3\" and python_version < \"3.6\" or python_version < \"3.6\""
 name = "pathlib2"
 optional = false
 python-versions = "*"
@@ -628,7 +645,6 @@ testing = ["nose", "coverage"]
 [[package]]
 category = "dev"
 description = "plugin and hook calling mechanisms for python"
-marker = "python_version < \"3\" or python_version >= \"3\""
 name = "pluggy"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
@@ -645,7 +661,6 @@ dev = ["pre-commit", "tox"]
 [[package]]
 category = "dev"
 description = "library with cross-python path, ini-parsing, io, code, log facilities"
-marker = "python_version < \"3\" or python_version >= \"3\""
 name = "py"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
@@ -695,7 +710,6 @@ version = "2.6.1"
 [[package]]
 category = "dev"
 description = "Python parsing module"
-marker = "python_version < \"3\" or python_version >= \"3\""
 name = "pyparsing"
 optional = false
 python-versions = ">=2.6, !=3.0.*, !=3.1.*, !=3.2.*"
@@ -865,7 +879,6 @@ setuptools = ">=40.0"
 [[package]]
 category = "dev"
 description = "World timezone definitions, modern and historical"
-marker = "python_version < \"3\" or python_version >= \"3\""
 name = "pytz"
 optional = false
 python-versions = "*"
@@ -1000,7 +1013,6 @@ version = "1.15.0"
 [[package]]
 category = "dev"
 description = "This package provides 26 stemmers for 25 languages generated from Snowball algorithms."
-marker = "python_version < \"3\" or python_version >= \"3\""
 name = "snowballstemmer"
 optional = false
 python-versions = "*"
@@ -1088,7 +1100,6 @@ tests = ["pytest", "mock"]
 [[package]]
 category = "dev"
 description = "sphinxcontrib-applehelp is a sphinx extension which outputs Apple help books"
-marker = "python_version >= \"3\""
 name = "sphinxcontrib-applehelp"
 optional = false
 python-versions = ">=3.5"
@@ -1101,7 +1112,6 @@ test = ["pytest"]
 [[package]]
 category = "dev"
 description = "sphinxcontrib-devhelp is a sphinx extension which outputs Devhelp document."
-marker = "python_version >= \"3\""
 name = "sphinxcontrib-devhelp"
 optional = false
 python-versions = ">=3.5"
@@ -1114,7 +1124,6 @@ test = ["pytest"]
 [[package]]
 category = "dev"
 description = "sphinxcontrib-htmlhelp is a sphinx extension which renders HTML help files"
-marker = "python_version >= \"3\""
 name = "sphinxcontrib-htmlhelp"
 optional = false
 python-versions = ">=3.5"
@@ -1127,7 +1136,6 @@ test = ["pytest", "html5lib"]
 [[package]]
 category = "dev"
 description = "A sphinx extension which renders display math in HTML via JavaScript"
-marker = "python_version >= \"3\""
 name = "sphinxcontrib-jsmath"
 optional = false
 python-versions = ">=3.5"
@@ -1139,7 +1147,6 @@ test = ["pytest", "flake8", "mypy"]
 [[package]]
 category = "dev"
 description = "sphinxcontrib-qthelp is a sphinx extension which outputs QtHelp document."
-marker = "python_version >= \"3\""
 name = "sphinxcontrib-qthelp"
 optional = false
 python-versions = ">=3.5"
@@ -1152,7 +1159,6 @@ test = ["pytest"]
 [[package]]
 category = "dev"
 description = "sphinxcontrib-serializinghtml is a sphinx extension which outputs \"serialized\" HTML files (json and pickle)."
-marker = "python_version >= \"3\""
 name = "sphinxcontrib-serializinghtml"
 optional = false
 python-versions = ">=3.5"
@@ -1177,7 +1183,6 @@ test = ["pytest", "mock"]
 [[package]]
 category = "dev"
 description = "Python Library for Tom's Obvious, Minimal Language"
-marker = "python_version >= \"3.6\" and python_version < \"4.0\" or python_version >= \"3\""
 name = "toml"
 optional = false
 python-versions = "*"
@@ -1255,6 +1260,15 @@ optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
 version = "3.7.4.3"
 
+[[package]]
+category = "dev"
+description = "Backported and Experimental Type Hints for Python 3.5+"
+marker = "python_version >= \"3.6\" and python_version < \"4.0\""
+name = "typing-extensions"
+optional = false
+python-versions = "*"
+version = "3.7.4.3"
+
 [[package]]
 category = "dev"
 description = "HTTP library with thread-safe connection pooling, file post, and more."
@@ -1293,7 +1307,7 @@ version = "0.5.1"
 [[package]]
 category = "dev"
 description = "Backport of pathlib-compatible object wrapper for zip files"
-marker = "python_version < \"3.8\" or python_version >= \"3\" and python_version < \"3.8\""
+marker = "python_version < \"3.8\" or python_version >= \"3\" and python_version < \"3.8\" or python_version >= \"3\" and python_version < \"3.8\" and (python_version < \"3.8\" or python_version >= \"3\" and python_version < \"3.8\")"
 name = "zipp"
 optional = false
 python-versions = ">=2.7"
@@ -1311,7 +1325,7 @@ testing = ["pathlib2", "unittest2", "jaraco.itertools", "func-timeout"]
 [[package]]
 category = "dev"
 description = "Backport of pathlib-compatible object wrapper for zip files"
-marker = "python_version >= \"3\" and python_version < \"3.8\" or python_version < \"3.8\""
+marker = "python_version >= \"3\" and python_version < \"3.8\" and (python_version < \"3.8\" or python_version >= \"3\" and python_version < \"3.8\") or python_version < \"3.8\" or python_version >= \"3\" and python_version < \"3.8\""
 name = "zipp"
 optional = false
 python-versions = ">=3.6"
@@ -1330,7 +1344,7 @@ lint = []
 test = []
 
 [metadata]
-content-hash = "55071e1712036e5feedbdbbd08b46a2ff50bd9691fb9bf1ef2ae44386833ec91"
+content-hash = "77432007847ff3d4dfb7b62412e8db50dfd30076ba6bb1e019851c7b0502e7ed"
 lock-version = "1.0"
 python-versions = "~2.7 || ^3.5"
 
@@ -1368,8 +1382,7 @@ babel = [
     {file = "backports.functools_lru_cache-1.6.1.tar.gz", hash = "sha256:8fde5f188da2d593bd5bc0be98d9abc46c95bb8a9dde93429570192ee6cc2d4a"},
 ]
 black = [
-    {file = "black-19.10b0-py36-none-any.whl", hash = "sha256:1b30e59be925fafc1ee4565e5e08abef6b03fe455102883820fe5ee2e4734e0b"},
-    {file = "black-19.10b0.tar.gz", hash = "sha256:c2edb73a08e9e0e6f65a0e6af18b059b8b1cdd5bef997d7a0b181df93dc81539"},
+    {file = "black-20.8b1.tar.gz", hash = "sha256:1c02557aa099101b9d21496f8a914e9ed2222ef70336404eeeac8edba836fbea"},
 ]
 bleach = [
     {file = "bleach-3.1.5-py2.py3-none-any.whl", hash = "sha256:2bce3d8fab545a6528c8fa5d9f9ae8ebc85a56da365c7f85180bfe96a35ef22f"},
@@ -1495,6 +1508,10 @@ cryptography = [
     {file = "cryptography-3.0-cp38-cp38-win_amd64.whl", hash = "sha256:bea0b0468f89cdea625bb3f692cd7a4222d80a6bdafd6fb923963f2b9da0e15f"},
     {file = "cryptography-3.0.tar.gz", hash = "sha256:8e924dbc025206e97756e8903039662aa58aa9ba357d8e1d8fc29e3092322053"},
 ]
+dataclasses = [
+    {file = "dataclasses-0.7-py3-none-any.whl", hash = "sha256:3459118f7ede7c8bea0fe795bff7c6c2ce287d01dd226202f7c9ebc0610a7836"},
+    {file = "dataclasses-0.7.tar.gz", hash = "sha256:494a6dcae3b8bcf80848eea2ef64c0cc5cd307ffc263e17cdf42f3e5420808e6"},
+]
 docutils = [
     {file = "docutils-0.16-py2.py3-none-any.whl", hash = "sha256:0c5b78adfbf7762415433f5515cd5c9e762339e23369dbe8000d84a4bf4ab3af"},
     {file = "docutils-0.16.tar.gz", hash = "sha256:c2de3a60e9e7d07be26b7f2b00ca0309c207e06c100f9cc2a94931fc75a478fc"},
@@ -1614,6 +1631,10 @@ more-itertools = [
     {file = "more-itertools-8.4.0.tar.gz", hash = "sha256:68c70cc7167bdf5c7c9d8f6954a7837089c6a36bf565383919bb595efb8a17e5"},
     {file = "more_itertools-8.4.0-py3-none-any.whl", hash = "sha256:b78134b2063dd214000685165d81c154522c3ee0a1c0d4d113c80361c234c5a2"},
 ]
+mypy-extensions = [
+    {file = "mypy_extensions-0.4.3-py2.py3-none-any.whl", hash = "sha256:090fedd75945a69ae91ce1303b5824f428daf5a028d2f6ab8a299250a846f15d"},
+    {file = "mypy_extensions-0.4.3.tar.gz", hash = "sha256:2d82818f5bb3e369420cb3c4060a7970edba416647068eb4c5343488a6c604a8"},
+]
 packaging = [
     {file = "packaging-20.4-py2.py3-none-any.whl", hash = "sha256:998416ba6962ae7fbd6596850b80e17859a5753ba17c32284f67bfff33784181"},
     {file = "packaging-20.4.tar.gz", hash = "sha256:4357f74f47b9c12db93624a82154e9b120fa8293699949152b22065d556079f8"},
@@ -1683,6 +1704,8 @@ pillow = [
     {file = "Pillow-7.2.0-cp38-cp38-manylinux2014_aarch64.whl", hash = "sha256:5e51ee2b8114def244384eda1c82b10e307ad9778dac5c83fb0943775a653cd8"},
     {file = "Pillow-7.2.0-cp38-cp38-win32.whl", hash = "sha256:725aa6cfc66ce2857d585f06e9519a1cc0ef6d13f186ff3447ab6dff0a09bc7f"},
     {file = "Pillow-7.2.0-cp38-cp38-win_amd64.whl", hash = "sha256:a060cf8aa332052df2158e5a119303965be92c3da6f2d93b6878f0ebca80b2f6"},
+    {file = "Pillow-7.2.0-pp36-pypy36_pp73-macosx_10_10_x86_64.whl", hash = "sha256:9c87ef410a58dd54b92424ffd7e28fd2ec65d2f7fc02b76f5e9b2067e355ebf6"},
+    {file = "Pillow-7.2.0-pp36-pypy36_pp73-manylinux2010_x86_64.whl", hash = "sha256:e901964262a56d9ea3c2693df68bc9860b8bdda2b04768821e4c44ae797de117"},
     {file = "Pillow-7.2.0-pp36-pypy36_pp73-win32.whl", hash = "sha256:25930fadde8019f374400f7986e8404c8b781ce519da27792cbe46eabec00c4d"},
     {file = "Pillow-7.2.0.tar.gz", hash = "sha256:97f9e7953a77d5a70f49b9a48da7776dc51e9b738151b22dacf101641594a626"},
 ]
@@ -1912,6 +1935,11 @@ typing = [
     {file = "typing-3.7.4.3-py2-none-any.whl", hash = "sha256:283d868f5071ab9ad873e5e52268d611e851c870a2ba354193026f2dfb29d8b5"},
     {file = "typing-3.7.4.3.tar.gz", hash = "sha256:1187fb9c82fd670d10aa07bbb6cfcfe4bdda42d6fab8d5134f04e8c4d0b71cc9"},
 ]
+typing-extensions = [
+    {file = "typing_extensions-3.7.4.3-py2-none-any.whl", hash = "sha256:dafc7639cde7f1b6e1acc0f457842a83e722ccca8eef5270af2d74792619a89f"},
+    {file = "typing_extensions-3.7.4.3-py3-none-any.whl", hash = "sha256:7cb407020f00f7bfc3cb3e7881628838e69d8f3fcab2f64742a5e76b2f841918"},
+    {file = "typing_extensions-3.7.4.3.tar.gz", hash = "sha256:99d4073b617d30288f569d3f13d2bd7548c3a7e4c8de87db09a9d29bb3a4a60c"},
+]
 urllib3 = [
     {file = "urllib3-1.25.10-py2.py3-none-any.whl", hash = "sha256:e7983572181f5e1522d9c98453462384ee92a0be7fac5f1413a1e35c56cc0461"},
     {file = "urllib3-1.25.10.tar.gz", hash = "sha256:91056c15fa70756691db97756772bb1eb9678fa585d9184f24534b100dc60f4a"},
diff --git a/pyproject.toml b/pyproject.toml
index d3a09729cf7..c636739c594 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -79,7 +79,7 @@ pytest-cov = [
 ]
 
 ### Format ###
-black = {version="==19.10b0", python="^3.6"}
+black = {version="==20.08b1", python="^3.6"}
 isort = [
   {version="<5", python="<3.6"},
   {version="*", python=">=3.6"}
diff --git a/tmuxp/cli.py b/tmuxp/cli.py
index 48045d361ec..eddcb95eb0d 100644
--- a/tmuxp/cli.py
+++ b/tmuxp/cli.py
@@ -37,9 +37,9 @@ def get_config_dir():
     """
     Return tmuxp configuration directory.
 
-    ``TMUXP_CONFIGDIR`` environmental variable has precedence if set. We also 
-    evaluate XDG default directory from XDG_CONFIG_HOME environmental variable 
-    if set or its default. Then the old default ~/.tmuxp is returned for 
+    ``TMUXP_CONFIGDIR`` environmental variable has precedence if set. We also
+    evaluate XDG default directory from XDG_CONFIG_HOME environmental variable
+    if set or its default. Then the old default ~/.tmuxp is returned for
     compatibility.
 
     Returns