diff --git a/ml_dtypes/_src/custom_float.h b/ml_dtypes/_src/custom_float.h
index 9f292eba..a4ffe6a5 100644
--- a/ml_dtypes/_src/custom_float.h
+++ b/ml_dtypes/_src/custom_float.h
@@ -850,7 +850,7 @@ bool RegisterFloatDtype(PyObject* numpy) {
   // bases must be a tuple for Python 3.9 and earlier. Change to just pass
   // the base type directly when dropping Python 3.9 support.
   Safe_PyObjectPtr bases(
-      PyTuple_Pack(1, reinterpret_cast<PyObject*>(&PyGenericArrType_Type)));
+      PyTuple_Pack(1, reinterpret_cast<PyObject*>(&PyFloatingArrType_Type)));
   PyObject* type =
       PyType_FromSpecWithBases(&CustomFloatType<T>::type_spec, bases.get());
   if (!type) {
diff --git a/ml_dtypes/_src/intn_numpy.h b/ml_dtypes/_src/intn_numpy.h
index e184e0b0..39e7ee73 100644
--- a/ml_dtypes/_src/intn_numpy.h
+++ b/ml_dtypes/_src/intn_numpy.h
@@ -769,7 +769,7 @@ bool RegisterIntNDtype(PyObject* numpy) {
   // bases must be a tuple for Python 3.9 and earlier. Change to just pass
   // the base type directly when dropping Python 3.9 support.
   Safe_PyObjectPtr bases(
-      PyTuple_Pack(1, reinterpret_cast<PyObject*>(&PyGenericArrType_Type)));
+      PyTuple_Pack(1, reinterpret_cast<PyObject*>(&PyIntegerArrType_Type)));
   PyObject* type =
       PyType_FromSpecWithBases(&IntNTypeDescriptor<T>::type_spec, bases.get());
   if (!type) {
diff --git a/ml_dtypes/tests/custom_float_test.py b/ml_dtypes/tests/custom_float_test.py
index 7eb313bb..e06e1cec 100644
--- a/ml_dtypes/tests/custom_float_test.py
+++ b/ml_dtypes/tests/custom_float_test.py
@@ -713,7 +713,7 @@ def testDeepCopyDoesNotAlterHash(self, float_type):
   def testArray(self, float_type):
     x = np.array([[1, 2, 4]], dtype=float_type)
     self.assertEqual(float_type, x.dtype)
-    self.assertEqual("[[1 2 4]]", str(x))
+    self.assertEqual("[[1. 2. 4.]]", str(x))
     np.testing.assert_equal(x, x)
     numpy_assert_allclose(x, x, float_type=float_type)
     self.assertTrue((x == x).all())
diff --git a/ml_dtypes/tests/intn_test.py b/ml_dtypes/tests/intn_test.py
index 86ab5a81..df02ab71 100644
--- a/ml_dtypes/tests/intn_test.py
+++ b/ml_dtypes/tests/intn_test.py
@@ -274,7 +274,7 @@ def testDeepCopyDoesNotAlterHash(self, scalar_type):
   def testArray(self, scalar_type):
     if scalar_type == int2:
       x = np.array([[-2, 1, 0, 1]], dtype=scalar_type)
-      self.assertEqual("[[-2 1 0 1]]", str(x))
+      self.assertEqual("[[-2  1  0  1]]", str(x))
     else:
       x = np.array([[1, 2, 3]], dtype=scalar_type)
       self.assertEqual("[[1 2 3]]", str(x))