diff --git a/pyproject.toml b/pyproject.toml
index f1f836b4..d810517a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -53,7 +53,7 @@ dependencies = [
     "einops>=0.8.0",
     "flask>=3.0.3",
     "gdown>=5.1.0",
-    "gymnasium==0.29.1",                                                 # TODO(rcadene, aliberts): Make gym 1.0.0 work
+    "gymnasium==0.29.1", # TODO(rcadene, aliberts): Make gym 1.0.0 work
     "h5py>=3.10.0",
     "huggingface-hub[hf-transfer,cli]>=0.27.1 ; python_version < '4.0'",
     "imageio[ffmpeg]>=2.34.0",
@@ -92,7 +92,7 @@ stretch = [
     "pyrealsense2>=2.55.1.6486 ; sys_platform != 'darwin'",
     "pynput>=1.7.7",
 ]
-test = ["pytest>=8.1.0", "pytest-cov>=5.0.0", "pyserial>=3.5"]
+test = ["pytest>=8.1.0", "pytest-cov>=5.0.0", "pyserial>=3.5", "mock-serial>=0.0.1 ; sys_platform != 'win32'"]
 umi = ["imagecodecs>=2024.1.1"]
 video_benchmark = ["scikit-image>=0.23.2", "pandas>=2.2.2"]
 xarm = ["gym-xarm>=0.1.1 ; python_version < '4.0'"]