diff --git a/pyproject.toml b/pyproject.toml
index 9ab736f9..751c9d41 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -113,5 +113,8 @@ addopts = """
 # Maps coverage measured in site-packages to source files in src
 source = ["src/", ".tox/*/lib/python*/site-packages/"]
 
+[tool.coverage.run]
+source = ["matplot2tikz"]
+
 [tool.coverage.html]
 directory = "reports/coverage_html"
diff --git a/tox.ini b/tox.ini
index dc4ab284..904c5309 100644
--- a/tox.ini
+++ b/tox.ini
@@ -13,7 +13,7 @@ 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
+    SETUPTOOLS_SHIM = 1
 commands =
     # Run tests from .py files
     pytest --typeguard-packages=matplot2tikz --junitxml=reports/pytest.xml.{envname} {posargs}