diff --git a/openslide/lowlevel.py b/openslide/lowlevel.py
index 22704c2d..7e771b5d 100644
--- a/openslide/lowlevel.py
+++ b/openslide/lowlevel.py
@@ -37,6 +37,8 @@
 import platform
 import sys
 
+from . import _convert
+
 if platform.system() == 'Windows':
     _lib = cdll.LoadLibrary('libopenslide-0.dll')
 elif platform.system() == 'Darwin':
@@ -57,58 +59,6 @@
 else:
     _lib = cdll.LoadLibrary('libopenslide.so.0')
 
-try:
-    from . import _convert
-    def _load_image(buf, size):
-        '''buf must be a mutable buffer.'''
-        _convert.argb2rgba(buf)
-        return PIL.Image.frombuffer('RGBA', size, buf, 'raw', 'RGBA', 0, 1)
-except ImportError:
-    def _load_image(buf, size):
-        '''buf must be a buffer.'''
-
-        # Load entire buffer at once if possible
-        MAX_PIXELS_PER_LOAD = (1 << 29) - 1
-        # Otherwise, use chunks smaller than the maximum to reduce memory
-        # requirements
-        PIXELS_PER_LOAD = 1 << 26
-
-        def do_load(buf, size):
-            '''buf can be a string, but should be a ctypes buffer to avoid an
-            extra copy in the caller.'''
-            # First reorder the bytes in a pixel from native-endian aRGB to
-            # big-endian RGBa to work around limitations in RGBa loader
-            rawmode = (sys.byteorder == 'little') and 'BGRA' or 'ARGB'
-            buf = PIL.Image.frombuffer('RGBA', size, buf, 'raw', rawmode, 0, 1)
-            # Image.tobytes() is named tostring() in Pillow 1.x and PIL
-            buf = (getattr(buf, 'tobytes', None) or buf.tostring)()
-            # Now load the image as RGBA, undoing premultiplication
-            return PIL.Image.frombuffer('RGBA', size, buf, 'raw', 'RGBa', 0, 1)
-
-        # Fast path for small buffers
-        w, h = size
-        if w * h <= MAX_PIXELS_PER_LOAD:
-            return do_load(buf, size)
-
-        # Load in chunks to avoid OverflowError in PIL.Image.frombuffer()
-        # https://github.com/python-pillow/Pillow/issues/1475
-        if w > PIXELS_PER_LOAD:
-            # We could support this, but it seems like overkill
-            raise ValueError('Width %d is too large (maximum %d)' %
-                    (w, PIXELS_PER_LOAD))
-        rows_per_load = PIXELS_PER_LOAD // w
-        img = PIL.Image.new('RGBA', (w, h))
-        for y in range(0, h, rows_per_load):
-            rows = min(h - y, rows_per_load)
-            if sys.version[0] == '2':
-                chunk = buffer(buf, 4 * y * w, 4 * rows * w)
-            else:
-                # PIL.Image.frombuffer() won't take a memoryview or
-                # bytearray, so we can't avoid copying
-                chunk = memoryview(buf)[y * w:(y + rows) * w].tobytes()
-            img.paste(do_load(chunk, (w, rows)), (0, y))
-        return img
-
 class OpenSlideError(Exception):
     """An error produced by the OpenSlide library.
 
@@ -167,6 +117,11 @@ def from_param(cls, obj):
         else:
             raise TypeError('Incorrect type')
 
+def _load_image(buf, size):
+    '''buf must be a mutable buffer.'''
+    _convert.argb2rgba(buf)
+    return PIL.Image.frombuffer('RGBA', size, buf, 'raw', 'RGBA', 0, 1)
+
 # check for errors opening an image file and wrap the resulting handle
 def _check_open(result, _func, _args):
     if result is None:
diff --git a/tests/__init__.py b/tests/__init__.py
index d2158b3d..3be04922 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -22,13 +22,6 @@
 from PIL import Image
 import unittest
 
-try:
-    import openslide._convert as _
-    have_optimizations = True
-except ImportError:
-    have_optimizations = False
-
-
 # PIL.Image cannot have zero width or height on Pillow 3.4.0 - 3.4.2
 # https://github.com/python-pillow/Pillow/issues/2259
 try:
diff --git a/tests/test_openslide.py b/tests/test_openslide.py
index f3d12df4..9b781368 100644
--- a/tests/test_openslide.py
+++ b/tests/test_openslide.py
@@ -25,8 +25,7 @@
 import sys
 import unittest
 
-from . import (file_path, have_optimizations, image_dimensions_cannot_be_zero,
-        skip_if)
+from . import file_path, image_dimensions_cannot_be_zero, skip_if
 
 # Tests should be written to be compatible with Python 2.6 unittest.
 
@@ -127,8 +126,7 @@ def test_read_region_bad_size(self):
     @skip_if(sys.maxsize < 1 << 32, '32-bit Python')
     # Broken on PIL and on Pillow >= 3.4.0, < 6.2.0.
     # https://github.com/python-pillow/Pillow/issues/3963
-    @skip_if(have_optimizations and
-            [int(i) for i in getattr(Image, '__version__', '0').split('.')] < [6,2,0],
+    @skip_if([int(i) for i in getattr(Image, '__version__', '0').split('.')] < [6,2,0],
             'broken on PIL and Pillow < 6.2.0')
     # Disabled to avoid OOM killer on small systems, since the stdlib
     # doesn't provide a way to find out how much RAM we have
@@ -137,12 +135,6 @@ def _test_read_region_2GB(self):
                 self.osr.read_region((1000, 1000), 0, (32768, 16384)).size,
                 (32768, 16384))
 
-    @skip_if(have_optimizations, 'only relevant --without-performance')
-    @skip_if(sys.maxsize < 1 << 32, '32-bit Python')
-    def test_read_region_2GB_width(self):
-        self.assertRaises(ValueError,
-                lambda: self.osr.read_region((1000, 1000), 0, (1 << 29, 1)))
-
     def test_thumbnail(self):
         self.assertEqual(self.osr.get_thumbnail((100, 100)).size, (100, 83))