diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index b9166a78..86b7111a 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -52,7 +52,7 @@ jobs:
 
     - name: Run tests
       run: |
-        pytest -v --cov=alchemlyb --cov-report=xml --color=yes src/alchemlyb/tests
+        pytest -v -n 2 --cov=alchemlyb --cov-report=xml --color=yes src/alchemlyb/tests
       env:
         MPLBACKEND: agg
 
diff --git a/devtools/conda-envs/test_env.yaml b/devtools/conda-envs/test_env.yaml
index dcb2f6cf..009c3c3a 100644
--- a/devtools/conda-envs/test_env.yaml
+++ b/devtools/conda-envs/test_env.yaml
@@ -5,7 +5,7 @@ dependencies:
 - python
 - numpy
 - pandas
-- pymbar
+- pymbar >=3.0.5,<4
 - scipy
 - scikit-learn
 - matplotlib
@@ -13,4 +13,5 @@ dependencies:
   # Testing
 - pytest
 - pytest-cov
+- pytest-xdist
 - codecov