diff --git a/src/array.rs b/src/array.rs
index 878c11ae3..f6907ea1e 100644
--- a/src/array.rs
+++ b/src/array.rs
@@ -16,9 +16,9 @@ use ndarray::{
 };
 use num_traits::AsPrimitive;
 use pyo3::{
-    ffi, pyobject_native_type_named, type_object, types::PyModule, AsPyPointer, FromPyObject,
-    IntoPy, Py, PyAny, PyClassInitializer, PyDowncastError, PyErr, PyNativeType, PyObject,
-    PyResult, PyTypeInfo, Python, ToPyObject,
+    ffi, pyobject_native_type_named, types::PyModule, AsPyPointer, FromPyObject, IntoPy, Py, PyAny,
+    PyClassInitializer, PyDowncastError, PyErr, PyNativeType, PyObject, PyResult, PyTypeInfo,
+    Python, ToPyObject,
 };
 
 use crate::borrow::{PyReadonlyArray, PyReadwriteArray};
@@ -95,6 +95,7 @@ use crate::slice_container::PySliceContainer;
 ///
 /// [ndarray]: https://numpy.org/doc/stable/reference/generated/numpy.ndarray.html
 /// [pyo3-memory]: https://pyo3.rs/main/memory.html
+#[repr(transparent)]
 pub struct PyArray<T, D>(PyAny, PhantomData<T>, PhantomData<D>);
 
 /// Zero-dimensional array.
@@ -119,10 +120,6 @@ pub fn get_array_module(py: Python<'_>) -> PyResult<&PyModule> {
     PyModule::import(py, npyffi::array::MOD_NAME)
 }
 
-unsafe impl<T, D> type_object::PyLayout<PyArray<T, D>> for npyffi::PyArrayObject {}
-
-impl<T, D> type_object::PySizedLayout<PyArray<T, D>> for npyffi::PyArrayObject {}
-
 unsafe impl<T: Element, D: Dimension> PyTypeInfo for PyArray<T, D> {
     type AsRefTarget = Self;
 
diff --git a/src/dtype.rs b/src/dtype.rs
index f7bc20bcd..9c008e213 100644
--- a/src/dtype.rs
+++ b/src/dtype.rs
@@ -45,6 +45,7 @@ pub use num_complex::{Complex32, Complex64};
 /// ```
 ///
 /// [dtype]: https://numpy.org/doc/stable/reference/generated/numpy.dtype.html
+#[repr(transparent)]
 pub struct PyArrayDescr(PyAny);
 
 pyobject_native_type_named!(PyArrayDescr);
@@ -61,12 +62,7 @@ unsafe impl PyTypeInfo for PyArrayDescr {
     }
 
     fn is_type_of(ob: &PyAny) -> bool {
-        unsafe {
-            ffi::PyObject_TypeCheck(
-                ob.as_ptr(),
-                PY_ARRAY_API.get_type_object(ob.py(), NpyTypes::PyArrayDescr_Type),
-            ) > 0
-        }
+        unsafe { ffi::PyObject_TypeCheck(ob.as_ptr(), Self::type_object_raw(ob.py())) > 0 }
     }
 }
 
diff --git a/src/npyffi/array.rs b/src/npyffi/array.rs
index 1470f8aac..5be9e0020 100644
--- a/src/npyffi/array.rs
+++ b/src/npyffi/array.rs
@@ -328,14 +328,15 @@ impl PyArrayAPI {
     impl_api![303; PyArray_SetWritebackIfCopyBase(arr: *mut PyArrayObject, base: *mut PyArrayObject) -> c_int];
 }
 
-// Define type objects that belongs to Numpy API
+// Define type objects associated with the NumPy API
 macro_rules! impl_array_type {
     ($(($offset:expr, $tname:ident)),*) => {
-        /// All type objects of numpy API.
+        /// All type objects exported by the NumPy API.
         #[allow(non_camel_case_types)]
         pub enum NpyTypes { $($tname),* }
+
         impl PyArrayAPI {
-            /// Get the pointer of the type object that `self` refers.
+            /// Get a pointer of the type object assocaited with `ty`.
             pub unsafe fn get_type_object(&self, py: Python, ty: NpyTypes) -> *mut PyTypeObject {
                 match ty {
                     $( NpyTypes::$tname => *(self.get(py, $offset)) as _ ),*
@@ -401,11 +402,11 @@ pub unsafe fn PyArray_CheckExact(py: Python, op: *mut PyObject) -> c_int {
 
 #[cfg(test)]
 mod tests {
-    use super::PY_ARRAY_API;
+    use super::*;
 
     #[test]
     fn call_api() {
-        pyo3::Python::with_gil(|py| unsafe {
+        Python::with_gil(|py| unsafe {
             assert_eq!(
                 PY_ARRAY_API.PyArray_MultiplyIntList(py, [1, 2, 3].as_mut_ptr(), 3),
                 6
diff --git a/src/npyffi/mod.rs b/src/npyffi/mod.rs
index aff5d1aba..d9026b22f 100644
--- a/src/npyffi/mod.rs
+++ b/src/npyffi/mod.rs
@@ -18,17 +18,17 @@ fn get_numpy_api(_py: Python, module: &str, capsule: &str) -> *const *const c_vo
     let module = CString::new(module).unwrap();
     let capsule = CString::new(capsule).unwrap();
     unsafe {
-        let numpy = ffi::PyImport_ImportModule(module.as_ptr());
-        assert!(!numpy.is_null(), "Failed to import numpy module");
-        let capsule = ffi::PyObject_GetAttrString(numpy as _, capsule.as_ptr());
-        assert!(!capsule.is_null(), "Failed to get numpy capsule API");
+        let module = ffi::PyImport_ImportModule(module.as_ptr());
+        assert!(!module.is_null(), "Failed to import NumPy module");
+        let capsule = ffi::PyObject_GetAttrString(module as _, capsule.as_ptr());
+        assert!(!capsule.is_null(), "Failed to get NumPy API capsule");
         ffi::PyCapsule_GetPointer(capsule, null_mut()) as _
     }
 }
 
-// Define Array&UFunc APIs
+// Implements wrappers for NumPy's Array and UFunc API
 macro_rules! impl_api {
-    [$offset: expr; $fname: ident ( $($arg: ident : $t: ty),* ) $( -> $ret: ty )* ] => {
+    [$offset: expr; $fname: ident ( $($arg: ident : $t: ty),* $(,)?) $( -> $ret: ty )* ] => {
         #[allow(non_snake_case)]
         pub unsafe fn $fname(&self, py: Python, $($arg : $t), *) $( -> $ret )* {
             let fptr = self.get(py, $offset)
@@ -36,10 +36,6 @@ macro_rules! impl_api {
             (*fptr)($($arg), *)
         }
     };
-    // To allow fn a(b: type,) -> ret
-    [$offset: expr; $fname: ident ( $($arg: ident : $t:ty,)* ) $( -> $ret: ty )* ] => {
-        impl_api![$offset; $fname( $($arg: $t),*) $( -> $ret )*];
-    }
 }
 
 pub mod array;
diff --git a/src/npyffi/ufunc.rs b/src/npyffi/ufunc.rs
index 50eb1d7c5..414538068 100644
--- a/src/npyffi/ufunc.rs
+++ b/src/npyffi/ufunc.rs
@@ -12,7 +12,7 @@ const MOD_NAME: &str = "numpy.core.umath";
 const CAPSULE_NAME: &str = "_UFUNC_API";
 
 /// A global variable which stores a ['capsule'](https://docs.python.org/3/c-api/capsule.html)
-/// pointer to [Numpy UFunc API](https://numpy.org/doc/stable/reference/c-api/array.html).
+/// pointer to [Numpy UFunc API](https://numpy.org/doc/stable/reference/c-api/ufunc.html).
 pub static PY_UFUNC_API: PyUFuncAPI = PyUFuncAPI::new();
 
 pub struct PyUFuncAPI {