diff --git a/environment.yml b/environment.yml
index 61ee7d40d..8b5510081 100644
--- a/environment.yml
+++ b/environment.yml
@@ -22,6 +22,7 @@ dependencies:
   - pytest-icdiff
   - robot_descriptions
   # [viz]
+  - lxml
   - mediapy
   - mujoco >= 3.0.0
   # System dependencies to run the tests
diff --git a/setup.cfg b/setup.cfg
index 633d071e0..32bc02968 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -75,6 +75,7 @@ testing =
     pytest-icdiff
     robot-descriptions
 viz =
+    lxml
     mediapy
     mujoco >= 3.0.0
 all =