diff --git a/pyproject.toml b/pyproject.toml
index 59af191..0dc6d41 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -31,10 +31,7 @@ dependencies = ["numpy~=1.22",
                 "scipy~=1.7", 
                 "thermopack~=2.2"]
 
-[project.optional-dependencies]
-test = ["pytest"]
-
 [tool.cibuildwheel]
 test-command = "pytest {project}/tests"
-test-requires = ["pytest"]
+test-requires = ["pytest", "matplotlib"]
 build-verbosity = 2
\ No newline at end of file
diff --git a/tests/test_flux_transforms.py b/tests/test_flux_transforms.py
index 72cd24e..33fdad7 100644
--- a/tests/test_flux_transforms.py
+++ b/tests/test_flux_transforms.py
@@ -2,7 +2,6 @@
 from scipy.constants import Avogadro, gas_constant
 from pykingas.HardSphere import HardSphere
 from pykingas.MieKinGas import MieKinGas
-import pytest
 import numpy as np
 from tools import models, check_eq