diff --git a/tox.ini b/tox.ini
index 69d62774..dc4ab284 100644
--- a/tox.ini
+++ b/tox.ini
@@ -12,6 +12,8 @@ package = wheel
 setenv =
     PY_IGNORE_IMPORTMISMATCH=1 # https://github.com/pytest-dev/pytest/issues/2042
     COVERAGE_FILE = reports{/}.coverage.{envname}
+    COVERAGE_PROCESS_START = {toxinidir}/pyproject.toml
+    PIP_PREFER_BINARY = True
 commands =
     # Run tests from .py files
     pytest --typeguard-packages=matplot2tikz --junitxml=reports/pytest.xml.{envname} {posargs}