diff --git a/build_tools/azure/posix.yml b/build_tools/azure/posix.yml
index c77c6e5b9f5dc..21d1371da1bd2 100644
--- a/build_tools/azure/posix.yml
+++ b/build_tools/azure/posix.yml
@@ -31,7 +31,8 @@ jobs:
     PILLOW_VERSION: 'latest'
     MATPLOTLIB_VERSION: 'latest'
     PYTEST_VERSION: 'latest'
-    PYTEST_XDIST_VERSION: 'latest'
+    # Disable pytest-xdist as it can stall builds
+    PYTEST_XDIST_VERSION: 'none'
     THREADPOOLCTL_VERSION: 'latest'
     COVERAGE: 'true'
     TEST_DOCSTRINGS: 'false'
diff --git a/build_tools/azure/windows.yml b/build_tools/azure/windows.yml
index 795ac391343df..f5cedae7fa060 100644
--- a/build_tools/azure/windows.yml
+++ b/build_tools/azure/windows.yml
@@ -17,8 +17,8 @@ jobs:
     JUNITXML: 'test-data.xml'
     SKLEARN_SKIP_NETWORK_TESTS: '1'
     PYTEST_VERSION: '5.2.1'
-    PYTEST_XDIST: 'true'
-    PYTEST_XDIST_VERSION: 'latest'
+    # Disable pytest-xdist as it can stall builds
+    PYTEST_XDIST_VERSION: 'none'
     TEST_DIR: '$(Agent.WorkFolder)/tmp_folder'
     SHOW_SHORT_SUMMARY: 'false'
     CPU_COUNT: '2'
diff --git a/sklearn/tree/_classes.py b/sklearn/tree/_classes.py
index b8eae3975e09d..533bf750da54d 100644
--- a/sklearn/tree/_classes.py
+++ b/sklearn/tree/_classes.py
@@ -253,7 +253,7 @@ def fit(self, X, y, sample_weight=None, check_input=True):
                 name="min_samples_leaf",
                 target_type=numbers.Real,
                 min_val=0.0,
-                include_boundaries="right",
+                include_boundaries="neither",
             )
             min_samples_leaf = int(ceil(self.min_samples_leaf * n_samples))