diff --git a/scripts/update_payload/applier.py b/scripts/update_payload/applier.py
index f5ae6b7..52a70f9 100644
--- a/scripts/update_payload/applier.py
+++ b/scripts/update_payload/applier.py
@@ -192,18 +192,23 @@
 
   """
 
-  def __init__(self, payload, bsdiff_in_place=True):
+  def __init__(self, payload, bsdiff_in_place=True,
+               truncate_to_expected_size=True):
     """Initialize the applier.
 
     Args:
       payload: the payload object to check
       bsdiff_in_place: whether to perform BSDIFF operation in-place (optional)
+      truncate_to_expected_size: whether to truncate the resulting partitions
+                                 to their expected sizes, as specified in the
+                                 payload (optional)
 
     """
     assert payload.is_init, 'uninitialized update payload'
     self.payload = payload
     self.block_size = payload.manifest.block_size
     self.bsdiff_in_place = bsdiff_in_place
+    self.truncate_to_expected_size = truncate_to_expected_size
 
   def _ApplyReplaceOperation(self, op, op_name, out_data, part_file, part_size):
     """Applies a REPLACE{,_BZ} operation.
@@ -430,6 +435,12 @@
     with open(new_part_file_name, 'r+b') as new_part_file:
       self._ApplyOperations(operations, base_name, new_part_file,
                             new_part_info.size)
+      # Truncate the result, if so instructed.
+      if self.truncate_to_expected_size:
+        new_part_file.seek(0, 2)
+        if new_part_file.tell() > new_part_info.size:
+          new_part_file.seek(new_part_info.size)
+          new_part_file.truncate()
 
     # Verify the resulting partition.
     with open(new_part_file_name, 'rb') as new_part_file:
diff --git a/scripts/update_payload/payload.py b/scripts/update_payload/payload.py
index 1796f51..0bac091 100644
--- a/scripts/update_payload/payload.py
+++ b/scripts/update_payload/payload.py
@@ -155,7 +155,7 @@
     self.is_init = True
 
   def Describe(self):
-
+    """Emits the payload embedded description data to standard output."""
     def _DescribeImageInfo(description, image_info):
       def _DisplayIndentedValue(name, value):
         print '  {:<14} {}'.format(name+':', value)
@@ -166,16 +166,18 @@
       _DisplayIndentedValue('Version', image_info.version)
       _DisplayIndentedValue('Key', image_info.key)
 
-      if (image_info.build_channel != image_info.channel):
+      if image_info.build_channel != image_info.channel:
         _DisplayIndentedValue('Build channel', image_info.build_channel)
 
-      if (image_info.build_version != image_info.version):
+      if image_info.build_version != image_info.version:
         _DisplayIndentedValue('Build version', image_info.build_version)
 
     if self.manifest.HasField('old_image_info'):
+      # pylint: disable=E1101
       _DescribeImageInfo('Old Image', self.manifest.old_image_info)
 
     if self.manifest.HasField('new_image_info'):
+      # pylint: disable=E1101
       _DescribeImageInfo('New Image', self.manifest.new_image_info)
 
   def _AssertInit(self):
@@ -230,7 +232,8 @@
                report_out_file=report_out_file)
 
   def Apply(self, new_kernel_part, new_rootfs_part, old_kernel_part=None,
-            old_rootfs_part=None, bsdiff_in_place=True):
+            old_rootfs_part=None, bsdiff_in_place=True,
+            truncate_to_expected_size=True):
     """Applies the update payload.
 
     Args:
@@ -239,6 +242,9 @@
       old_kernel_part: name of source kernel partition file (optional)
       old_rootfs_part: name of source rootfs partition file (optional)
       bsdiff_in_place: whether to perform BSDIFF operations in-place (optional)
+      truncate_to_expected_size: whether to truncate the resulting partitions
+                                 to their expected sizes, as specified in the
+                                 payload (optional)
     Raises:
       PayloadError if payload application failed.
 
@@ -246,7 +252,9 @@
     self._AssertInit()
 
     # Create a short-lived payload applier object and run it.
-    helper = applier.PayloadApplier(self, bsdiff_in_place=bsdiff_in_place)
+    helper = applier.PayloadApplier(
+        self, bsdiff_in_place=bsdiff_in_place,
+        truncate_to_expected_size=truncate_to_expected_size)
     helper.Run(new_kernel_part, new_rootfs_part,
                old_kernel_part=old_kernel_part,
                old_rootfs_part=old_rootfs_part)