diff --git a/dask_sql/physical/rel/custom/wrappers.py b/dask_sql/physical/rel/custom/wrappers.py
index c6432497b..244d2ff42 100644
--- a/dask_sql/physical/rel/custom/wrappers.py
+++ b/dask_sql/physical/rel/custom/wrappers.py
@@ -17,6 +17,8 @@
 from sklearn.metrics import make_scorer
 from sklearn.utils.validation import check_is_fitted
 
+from dask_sql.utils import make_pickable_without_dask_sql
+
 try:
     import sklearn.base
     import sklearn.metrics
@@ -198,10 +200,14 @@ def transform(self, X):
         if isinstance(X, da.Array):
             if output_meta is None:
                 output_meta = _get_output_dask_ar_meta_for_estimator(
-                    _transform, self._postfit_estimator, X
+                    _transform,
+                    self._postfit_estimator,
+                    X,
                 )
             return X.map_blocks(
-                _transform, estimator=self._postfit_estimator, meta=output_meta
+                _transform,
+                estimator=self._postfit_estimator,
+                meta=output_meta,
             )
         elif isinstance(X, dd._Frame):
             if output_meta is None:
@@ -219,7 +225,9 @@ def transform(self, X):
                     # for infering meta
                     output_meta = dd.core.no_default
                 return X.map_partitions(
-                    _transform, estimator=self._postfit_estimator, meta=output_meta
+                    _transform,
+                    estimator=self._postfit_estimator,
+                    meta=output_meta,
                 )
         else:
             return _transform(X, estimator=self._postfit_estimator)
@@ -315,7 +323,9 @@ def predict(self, X):
                 if output_meta is None:
                     output_meta = dd.core.no_default
                 return X.map_partitions(
-                    _predict, estimator=self._postfit_estimator, meta=output_meta
+                    _predict,
+                    estimator=self._postfit_estimator,
+                    meta=output_meta,
                 )
         else:
             return _predict(X, estimator=self._postfit_estimator)
@@ -553,6 +563,7 @@ def partial_fit(self, X, y=None, **fit_kwargs):
         return self._fit_for_estimator(estimator, X, y, **fit_kwargs)
 
 
+@make_pickable_without_dask_sql
 def _predict(part, estimator, output_meta=None):
     if part.shape[0] == 0 and output_meta is not None:
         empty_output = handle_empty_partitions(output_meta)
@@ -561,6 +572,7 @@ def _predict(part, estimator, output_meta=None):
     return estimator.predict(part)
 
 
+@make_pickable_without_dask_sql
 def _predict_proba(part, estimator, output_meta=None):
     if part.shape[0] == 0 and output_meta is not None:
         empty_output = handle_empty_partitions(output_meta)
@@ -569,6 +581,7 @@ def _predict_proba(part, estimator, output_meta=None):
     return estimator.predict_proba(part)
 
 
+@make_pickable_without_dask_sql
 def _transform(part, estimator, output_meta=None):
     if part.shape[0] == 0 and output_meta is not None:
         empty_output = handle_empty_partitions(output_meta)
diff --git a/tests/unit/test_ml_wrappers.py b/tests/unit/test_ml_wrappers.py
index 97277c1ad..0f02707b0 100644
--- a/tests/unit/test_ml_wrappers.py
+++ b/tests/unit/test_ml_wrappers.py
@@ -17,6 +17,8 @@
 
 from dask_sql.physical.rel.custom.wrappers import Incremental, ParallelPostFit
 
+from ..integration.fixtures import skip_if_external_scheduler
+
 
 def _check_axis_partitioning(chunks, n_features):
     c = chunks[1][0]
@@ -123,6 +125,7 @@ def assert_estimator_equal(left, right, exclude=None, **kwargs):
         _assert_eq(l, r, name=attr, **kwargs)
 
 
+@skip_if_external_scheduler
 def test_parallelpostfit_basic():
     clf = ParallelPostFit(GradientBoostingClassifier())
 
@@ -194,6 +197,7 @@ def test_transform(kind):
     assert_eq_ar(result, expected)
 
 
+@skip_if_external_scheduler
 @pytest.mark.parametrize("dataframes", [False, True])
 def test_incremental_basic(dataframes):
     # Create observations that we know linear models can recover