diff --git a/poetry.lock b/poetry.lock
index a1eb9bd..333ab22 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -637,7 +637,7 @@ testing = ["pytest (>=4.6)", "pytest-checkdocs (>=1.2.3)", "pytest-flake8", "pyt
 [metadata]
 content-hash = "d7061a714fbdc1ec52f765b2818605719206466c4bc867ba31fc805250b4a97e"
 lock-version = "1.0"
-python-versions = "^3.9"
+python-versions = "^3.8"
 
 [metadata.files]
 appdirs = [
diff --git a/pyproject.toml b/pyproject.toml
index f5a70a8..a348018 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -9,7 +9,7 @@ packages = [
 ]
 
 [tool.poetry.dependencies]
-python = "^3.9"
+python = "^3.8"
 requests = "^2.25.1"
 attrs = "^21.2.0"
 cattrs = "^1.7.1"
diff --git a/tox.ini b/tox.ini
index a436de8..65eb78b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,7 @@
 # For more information about tox, see https://tox.readthedocs.io/en/latest/
 [tox]
-envlist = py37,py38,py39,flake8
+envlist = py38,py39,flake8
+isolated_build = True
 
 [testenv]
 ;changedir=tests