diff --git a/poetry.lock b/poetry.lock
index 9015e4f1..eebda809 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -427,7 +427,7 @@ restructuredtext-lint = "*"
 
 [[package]]
 name = "furo"
-version = "2021.4.11b34"
+version = "2021.6.18b36"
 description = "A clean customisable Sphinx documentation theme."
 category = "dev"
 optional = false
@@ -435,7 +435,7 @@ python-versions = ">=3.6"
 
 [package.dependencies]
 beautifulsoup4 = "*"
-sphinx = ">=3.0,<4.0"
+sphinx = ">=3.0,<5.0"
 
 [package.extras]
 doc = ["myst-parser", "sphinx-copybutton", "sphinx-inline-tabs", "docutils (!=0.17)"]
@@ -1374,7 +1374,7 @@ testing = ["pytest (>=4.6)", "pytest-checkdocs (>=1.2.3)", "pytest-flake8", "pyt
 [metadata]
 lock-version = "1.1"
 python-versions = "^3.6.1"
-content-hash = "0f80c50ac037b9628484d4478e876f9e7673d7fa71103bd2cada9e9351fec3f1"
+content-hash = "b9d64eb45f66049357f10352d035f88e54495f9807498711c6332e968dbd3e64"
 
 [metadata.files]
 alabaster = [
@@ -1632,8 +1632,8 @@ flake8-rst-docstrings = [
     {file = "flake8_rst_docstrings-0.2.3-py3-none-any.whl", hash = "sha256:565bbb391d7e4d0042924102221e9857ad72929cdd305b26501736ec22c1451a"},
 ]
 furo = [
-    {file = "furo-2021.4.11b34-py3-none-any.whl", hash = "sha256:576a1dc1bcbe337d7c53cbc75b886802778a5964fd2e3324433d706066e9aea8"},
-    {file = "furo-2021.4.11b34.tar.gz", hash = "sha256:3d88e2855949cecf5f562e8a28cab1a6d3355d82f3cf5796eddf9ec234e97519"},
+    {file = "furo-2021.6.18b36-py3-none-any.whl", hash = "sha256:a4c00634afeb5896a34d141a5dffb62f20c5eca7831b78269823a8cd8b09a5e4"},
+    {file = "furo-2021.6.18b36.tar.gz", hash = "sha256:46a30bc597a9067088d39d730e7d9bf6c1a1d71967e4af062f796769f66b3bdb"},
 ]
 gitdb = [
     {file = "gitdb-4.0.5-py3-none-any.whl", hash = "sha256:91f36bfb1ab7949b3b40e23736db18231bf7593edada2ba5c3a174a7b23657ac"},
diff --git a/pyproject.toml b/pyproject.toml
index ae473022..9089a2e1 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -45,7 +45,7 @@ pep8-naming = "^0.11.1"
 darglint = "^1.8.0"
 reorder-python-imports = "^2.5.0"
 pre-commit-hooks = "^4.0.1"
-furo = "^2021.4.11b34"
+furo = "^2021.6.18b36"
 Pygments = "^2.9.0"
 poetry = "^1.1.6"
 pytest-datadir = "^1.3.1"