--- nml-0.4.2/nml/lz77.py
+++ nml-0.4.2/nml/lz77.py
@@ -25,7 +25,7 @@
     @return: Compressed data.
     @rtype:  C{bytearray}
     """
-    stream = data.tostring()
+    stream = data.tobytes()
     position = 0
     output = array.array('B')
     literal_bytes = array.array('B')
--- nml-0.4.2/nml/spriteencoder.py
+++ nml-0.4.2/nml/spriteencoder.py
@@ -276,7 +276,7 @@
                 pos = generic.build_position(sprite_info.poslist)
                 raise generic.ScriptError("Read beyond bounds of image file '{}'".format(filename_32bpp.value), pos)
             sprite = im.crop((x, y, x + size_x, y + size_y))
-            rgb_sprite_data = sprite.tostring()
+            rgb_sprite_data = sprite.tobytes()
 
             if (info_byte & INFO_ALPHA) != 0:
                 # Check for half-transparent pixels (not valid for ground sprites)
@@ -296,7 +296,7 @@
                 raise generic.ScriptError("Read beyond bounds of image file '{}'".format(filename_8bpp.value), pos)
             mask_sprite = mask_im.crop((mask_x, mask_y, mask_x + size_x, mask_y + size_y))
 
-            mask_sprite_data = self.palconvert(mask_sprite.tostring(), im_mask_pal)
+            mask_sprite_data = self.palconvert(mask_sprite.tobytes(), im_mask_pal)
 
             # Check for white pixels; those that cause "artefacts" when shading
             pixel_stats['white'] = sum(p == 255 for p in mask_sprite_data)