diff --git a/include/boost/python/numpy/dtype.hpp b/include/boost/python/numpy/dtype.hpp
index 4673745e57..d7831f87dc 100644
--- a/include/boost/python/numpy/dtype.hpp
+++ b/include/boost/python/numpy/dtype.hpp
@@ -47,7 +47,7 @@ class BOOST_NUMPY_DECL dtype : public object {
   template <typename T> static dtype get_builtin();
 
   /// @brief Return the size of the data type in bytes.
-  int get_itemsize() const;
+  boost::python::ssize_t get_itemsize() const;
 
   /**
    *  @brief Compare two dtypes for equivalence.
diff --git a/src/numpy/dtype.cpp b/src/numpy/dtype.cpp
index 1ce8c6ec32..3985af6046 100644
--- a/src/numpy/dtype.cpp
+++ b/src/numpy/dtype.cpp
@@ -98,7 +98,7 @@ python::detail::new_reference dtype::convert(object const & arg, bool align)
   return python::detail::new_reference(reinterpret_cast<PyObject*>(obj));
 }
 
-int dtype::get_itemsize() const {
+boost::python::ssize_t dtype::get_itemsize() const {
 #if NPY_ABI_VERSION < 0x02000000
   return reinterpret_cast<PyArray_Descr*>(ptr())->elsize;
 #else
diff --git a/src/numpy/ndarray.cpp b/src/numpy/ndarray.cpp
index af09ecc338..a85e2520ab 100644
--- a/src/numpy/ndarray.cpp
+++ b/src/numpy/ndarray.cpp
@@ -41,11 +41,15 @@ int bitflag_to_numpy(ndarray::bitflag f)
 
 bool is_c_contiguous(std::vector<Py_intptr_t> const & shape,
 		     std::vector<Py_intptr_t> const & strides,
-		     int itemsize)
-{
-  std::vector<Py_intptr_t>::const_reverse_iterator j = strides.rbegin();
-  int total = itemsize;
-  for (std::vector<Py_intptr_t>::const_reverse_iterator i = shape.rbegin(); i != shape.rend(); ++i, ++j) 
+		     boost::python::ssize_t const itemsize)
+{
+  // An itemsize less than 0 is not useful - default to non-contiguity.
+  if (0 > itemsize) return false;
+  // Check the strides (stride[n]) match the accumulated shapes as per C-style,
+  // i.e. starting from rightmost C-index (itemsize * prod_{i in [n, N)} shape[i]).
+  std::vector<Py_intptr_t>::const_reverse_iterator j = strides.crbegin();
+  boost::python::ssize_t total = itemsize;
+  for (std::vector<Py_intptr_t>::const_reverse_iterator i = shape.crbegin(); i != shape.crend(); ++i, ++j)
   {
     if (total != *j) return false;
     total *= (*i);
@@ -55,11 +59,15 @@ bool is_c_contiguous(std::vector<Py_intptr_t> const & shape,
 
 bool is_f_contiguous(std::vector<Py_intptr_t> const & shape,
 		     std::vector<Py_intptr_t> const & strides,
-		     int itemsize)
-{
-  std::vector<Py_intptr_t>::const_iterator j = strides.begin();
-  int total = itemsize;
-  for (std::vector<Py_intptr_t>::const_iterator i = shape.begin(); i != shape.end(); ++i, ++j)
+		     boost::python::ssize_t const itemsize)
+{
+  // An itemsize less than 0 is not useful - default to non-contiguity.
+  if (0 > itemsize) return false;
+  // Check the strides (stride[n]) match the accumulated shapes as per Fortran-style,
+  // i.e. starting from leftmost C-index (itemsize * prod_{i in [0, n]} shape[i]).
+  std::vector<Py_intptr_t>::const_iterator j = strides.cbegin();
+  boost::python::ssize_t total = itemsize;
+  for (std::vector<Py_intptr_t>::const_iterator i = shape.cbegin(); i != shape.cend(); ++i, ++j)
   {
     if (total != *j) return false;
     total *= (*i);
@@ -68,9 +76,12 @@ bool is_f_contiguous(std::vector<Py_intptr_t> const & shape,
 }
 
 bool is_aligned(std::vector<Py_intptr_t> const & strides,
-		int itemsize)
+		boost::python::ssize_t const itemsize)
 {
-  for (std::vector<Py_intptr_t>::const_iterator i = strides.begin(); i != strides.end(); ++i) 
+  // An itemsize less than 0 is not useful - default to non-aligned.
+  if (0 > itemsize) return false;
+  // Check all strides to be aligned to itemsize.
+  for (std::vector<Py_intptr_t>::const_iterator i = strides.cbegin(); i != strides.cend(); ++i)
   {
     if (*i % itemsize) return false;
   }
@@ -117,7 +128,7 @@ ndarray from_data_impl(void * data,
     PyErr_SetString(PyExc_ValueError, "Length of shape and strides arrays do not match.");
     python::throw_error_already_set();
   }
-  int itemsize = dt.get_itemsize();
+  boost::python::ssize_t const itemsize = dt.get_itemsize();
   int flags = 0;
   if (writeable) flags |= NPY_ARRAY_WRITEABLE;
   if (is_c_contiguous(shape, strides, itemsize)) flags |= NPY_ARRAY_C_CONTIGUOUS;