diff --git a/pysindy/feature_library/base.py b/pysindy/feature_library/base.py
index 16149b27c..54697da45 100644
--- a/pysindy/feature_library/base.py
+++ b/pysindy/feature_library/base.py
@@ -63,10 +63,9 @@ def correct_shape(self, x: AxesArray):
         return x
 
     def calc_trajectory(self, diff_method, x, t):
-        axes = x.__dict__
         x_dot = diff_method(x, t=t)
-        x = AxesArray(diff_method.smoothed_x_, axes)
-        return x, AxesArray(x_dot, axes)
+        x = AxesArray(diff_method.smoothed_x_, x.axes)
+        return x, AxesArray(x_dot, x.axes)
 
     def get_spatial_grid(self):
         return None
@@ -337,7 +336,7 @@ def __init__(
         self.libraries = libraries
         self.inputs_per_library = inputs_per_library
 
-    def _combinations(self, lib_i, lib_j):
+    def _combinations(self, lib_i: AxesArray, lib_j: AxesArray) -> AxesArray:
         """
         Compute combinations of the numerical libraries.
 
@@ -351,7 +350,7 @@ def _combinations(self, lib_i, lib_j):
             lib_i.shape[lib_i.ax_coord] * lib_j.shape[lib_j.ax_coord]
         )
         lib_full = np.reshape(
-            lib_i[..., :, np.newaxis] * lib_j[..., np.newaxis, :],
+            lib_i[..., :, "coord"] * lib_j[..., "coord", :],
             shape,
         )
 
diff --git a/pysindy/feature_library/generalized_library.py b/pysindy/feature_library/generalized_library.py
index 3e5e24055..29834c2a8 100644
--- a/pysindy/feature_library/generalized_library.py
+++ b/pysindy/feature_library/generalized_library.py
@@ -237,7 +237,7 @@ def transform(self, x_full):
                 else:
                     xps.append(lib.transform([x])[0])
 
-            xp = AxesArray(np.concatenate(xps, axis=xps[0].ax_coord), xps[0].__dict__)
+            xp = AxesArray(np.concatenate(xps, axis=xps[0].ax_coord), xps[0].axes)
             xp_full = xp_full + [xp]
         return xp_full
 
diff --git a/pysindy/feature_library/polynomial_library.py b/pysindy/feature_library/polynomial_library.py
index 75dbf5637..e62af38bd 100644
--- a/pysindy/feature_library/polynomial_library.py
+++ b/pysindy/feature_library/polynomial_library.py
@@ -225,7 +225,7 @@ def transform(self, x_full):
                         dtype=x.dtype,
                         order=self.order,
                     ),
-                    x.__dict__,
+                    x.axes,
                 )
                 for i, comb in enumerate(combinations):
                     xp[..., i] = x[..., comb].prod(-1)
diff --git a/pysindy/feature_library/sindy_pi_library.py b/pysindy/feature_library/sindy_pi_library.py
index 8d5f054a7..f45cf567f 100644
--- a/pysindy/feature_library/sindy_pi_library.py
+++ b/pysindy/feature_library/sindy_pi_library.py
@@ -404,5 +404,5 @@ def transform(self, x_full):
                                     *[x[:, comb] for comb in f_combs]
                                 ) * f_dot(*[x_dot[:, comb] for comb in f_dot_combs])
                                 library_idx += 1
-            xp_full = xp_full + [AxesArray(xp, x.__dict__)]
+            xp_full = xp_full + [AxesArray(xp, x.axes)]
         return xp_full
diff --git a/pysindy/optimizers/base.py b/pysindy/optimizers/base.py
index 45d4842b2..614341b54 100644
--- a/pysindy/optimizers/base.py
+++ b/pysindy/optimizers/base.py
@@ -144,7 +144,8 @@ def fit(self, x_, y, sample_weight=None, **reduce_kws):
         self : returns an instance of self
         """
         x_ = AxesArray(np.asarray(x_), {"ax_sample": 0, "ax_coord": 1})
-        y = AxesArray(np.asarray(y), {"ax_sample": 0, "ax_coord": 1})
+        y_axes = {"ax_sample": 0} if y.ndim == 1 else {"ax_sample": 0, "ax_coord": 1}
+        y = AxesArray(np.asarray(y), y_axes)
         x_, y = drop_nan_samples(x_, y)
         x_, y = check_X_y(x_, y, accept_sparse=[], y_numeric=True, multi_output=True)
 
diff --git a/test/test_feature_library.py b/test/test_feature_library.py
index 8e98b1a0d..6fba611a5 100644
--- a/test/test_feature_library.py
+++ b/test/test_feature_library.py
@@ -247,6 +247,7 @@ def test_sindypi_library_bad_params(params):
         pytest.lazy_fixture("ode_library"),
         pytest.lazy_fixture("sindypi_library"),
     ],
+    ids=type,
 )
 def test_fit_transform(data_lorenz, library):
     x, t = data_lorenz
diff --git a/test/test_optimizers.py b/test/test_optimizers.py
index c69ce9823..7bd657aa1 100644
--- a/test/test_optimizers.py
+++ b/test/test_optimizers.py
@@ -587,7 +587,7 @@ def test_specific_bad_parameters(error, optimizer, params, data_lorenz):
 def test_bad_optimizers(data_derivative_1d):
     x, x_dot = data_derivative_1d
     x = x.reshape(-1, 1)
-
+    x_dot = x_dot.reshape(-1, 1)
     with pytest.raises(InvalidParameterError):
         # Error: optimizer does not have a callable fit method
         opt = WrappedOptimizer(DummyEmptyModel())