diff --git a/scripts/update_payload/applier.py b/scripts/update_payload/applier.py
index e3708c7..fa419bd 100644
--- a/scripts/update_payload/applier.py
+++ b/scripts/update_payload/applier.py
@@ -195,14 +195,14 @@
   """
 
   def __init__(self, payload, bsdiff_in_place=True, bspatch_path=None,
-               imgpatch_path=None, truncate_to_expected_size=True):
+               puffpatch_path=None, 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)
       bspatch_path: path to the bspatch binary (optional)
-      imgpatch_path: path to the imgpatch binary (optional)
+      puffpatch_path: path to the puffpatch binary (optional)
       truncate_to_expected_size: whether to truncate the resulting partitions
                                  to their expected sizes, as specified in the
                                  payload (optional)
@@ -213,7 +213,7 @@
     self.minor_version = payload.manifest.minor_version
     self.bsdiff_in_place = bsdiff_in_place
     self.bspatch_path = bspatch_path or 'bspatch'
-    self.imgpatch_path = imgpatch_path or 'imgpatch'
+    self.puffpatch_path = puffpatch_path or 'imgpatch'
     self.truncate_to_expected_size = truncate_to_expected_size
 
   def _ApplyReplaceOperation(self, op, op_name, out_data, part_file, part_size):
@@ -347,7 +347,7 @@
 
   def _ApplyDiffOperation(self, op, op_name, patch_data, old_part_file,
                           new_part_file):
-    """Applies a SOURCE_BSDIFF or IMGDIFF operation.
+    """Applies a SOURCE_BSDIFF or PUFFDIFF operation.
 
     Args:
       op: the operation object
@@ -373,7 +373,7 @@
 
     if (hasattr(new_part_file, 'fileno') and
         ((not old_part_file) or hasattr(old_part_file, 'fileno')) and
-        op.type != common.OpType.IMGDIFF):
+        op.type != common.OpType.PUFFDIFF):
       # Construct input and output extents argument for bspatch.
       in_extents_arg, _, _ = _ExtentsToBspatchArg(
           op.src_extents, block_size, '%s.src_extents' % op_name,
@@ -411,8 +411,8 @@
       # Invoke bspatch.
       patch_cmd = [self.bspatch_path, in_file_name, out_file_name,
                    patch_file_name]
-      if op.type == common.OpType.IMGDIFF:
-        patch_cmd[0] = self.imgpatch_path
+      if op.type == common.OpType.PUFFDIFF:
+        patch_cmd[0] = self.puffpatch_path
       subprocess.check_call(patch_cmd)
 
       # Read output.
@@ -468,7 +468,7 @@
       elif op.type == common.OpType.SOURCE_COPY:
         self._ApplySourceCopyOperation(op, op_name, old_part_file,
                                        new_part_file)
-      elif op.type in (common.OpType.SOURCE_BSDIFF, common.OpType.IMGDIFF):
+      elif op.type in (common.OpType.SOURCE_BSDIFF, common.OpType.PUFFDIFF):
         self._ApplyDiffOperation(op, op_name, data, old_part_file,
                                  new_part_file)
       else:
@@ -504,7 +504,7 @@
         shutil.copyfile(old_part_file_name, new_part_file_name)
       elif (self.minor_version == common.SOURCE_MINOR_PAYLOAD_VERSION or
             self.minor_version == common.OPSRCHASH_MINOR_PAYLOAD_VERSION or
-            self.minor_version == common.IMGDIFF_MINOR_PAYLOAD_VERSION):
+            self.minor_version == common.PUFFDIFF_MINOR_PAYLOAD_VERSION):
         # In minor version >= 2, we don't want to copy the partitions, so
         # instead just make the new partition file.
         open(new_part_file_name, 'w').close()
diff --git a/scripts/update_payload/checker.py b/scripts/update_payload/checker.py
index e13ea13..3144395 100644
--- a/scripts/update_payload/checker.py
+++ b/scripts/update_payload/checker.py
@@ -816,7 +816,7 @@
       raise error.PayloadError('%s: excess dst blocks.' % op_name)
 
   def _CheckAnyDiffOperation(self, data_length, total_dst_blocks, op_name):
-    """Specific checks for BSDIFF, SOURCE_BSDIFF and IMGDIFF operations.
+    """Specific checks for BSDIFF, SOURCE_BSDIFF and PUFFDIFF operations.
 
     Args:
       data_length: The length of the data blob associated with the operation.
@@ -981,7 +981,7 @@
     elif op.type == common.OpType.SOURCE_BSDIFF and self.minor_version >= 2:
       self._CheckAnyDiffOperation(data_length, total_dst_blocks, op_name)
       self._CheckAnySourceOperation(op, total_src_blocks, op_name)
-    elif op.type == common.OpType.IMGDIFF and self.minor_version >= 4:
+    elif op.type == common.OpType.PUFFDIFF and self.minor_version >= 4:
       self._CheckAnyDiffOperation(data_length, total_dst_blocks, op_name)
       self._CheckAnySourceOperation(op, total_src_blocks, op_name)
     else:
@@ -1041,7 +1041,7 @@
         common.OpType.BSDIFF: 0,
         common.OpType.SOURCE_COPY: 0,
         common.OpType.SOURCE_BSDIFF: 0,
-        common.OpType.IMGDIFF: 0,
+        common.OpType.PUFFDIFF: 0,
     }
     # Total blob sizes for each operation type.
     op_blob_totals = {
@@ -1051,7 +1051,7 @@
         common.OpType.BSDIFF: 0,
         # SOURCE_COPY operations don't have blobs.
         common.OpType.SOURCE_BSDIFF: 0,
-        common.OpType.IMGDIFF: 0,
+        common.OpType.PUFFDIFF: 0,
     }
     # Counts of hashed vs unhashed operations.
     blob_hash_counts = {
diff --git a/scripts/update_payload/checker_unittest.py b/scripts/update_payload/checker_unittest.py
index 56b1a30..a0a5056 100755
--- a/scripts/update_payload/checker_unittest.py
+++ b/scripts/update_payload/checker_unittest.py
@@ -38,7 +38,7 @@
       'ZERO': common.OpType.ZERO,
       'DISCARD': common.OpType.DISCARD,
       'REPLACE_XZ': common.OpType.REPLACE_XZ,
-      'IMGDIFF': common.OpType.IMGDIFF,
+      'PUFFDIFF': common.OpType.PUFFDIFF,
   }
   return op_name_to_type[op_name]
 
diff --git a/scripts/update_payload/common.py b/scripts/update_payload/common.py
index 678fc5d..bab8a4f 100644
--- a/scripts/update_payload/common.py
+++ b/scripts/update_payload/common.py
@@ -27,7 +27,7 @@
 INPLACE_MINOR_PAYLOAD_VERSION = 1
 SOURCE_MINOR_PAYLOAD_VERSION = 2
 OPSRCHASH_MINOR_PAYLOAD_VERSION = 3
-IMGDIFF_MINOR_PAYLOAD_VERSION = 4
+PUFFDIFF_MINOR_PAYLOAD_VERSION = 4
 
 #
 # Payload operation types.
@@ -45,9 +45,9 @@
   ZERO = _CLASS.ZERO
   DISCARD = _CLASS.DISCARD
   REPLACE_XZ = _CLASS.REPLACE_XZ
-  IMGDIFF = _CLASS.IMGDIFF
+  PUFFDIFF = _CLASS.PUFFDIFF
   ALL = (REPLACE, REPLACE_BZ, MOVE, BSDIFF, SOURCE_COPY, SOURCE_BSDIFF, ZERO,
-         DISCARD, REPLACE_XZ, IMGDIFF)
+         DISCARD, REPLACE_XZ, PUFFDIFF)
   NAMES = {
       REPLACE: 'REPLACE',
       REPLACE_BZ: 'REPLACE_BZ',
@@ -58,7 +58,7 @@
       ZERO: 'ZERO',
       DISCARD: 'DISCARD',
       REPLACE_XZ: 'REPLACE_XZ',
-      IMGDIFF: 'IMGDIFF',
+      PUFFDIFF: 'PUFFDIFF',
   }
 
   def __init__(self):
diff --git a/scripts/update_payload/update_metadata_pb2.py b/scripts/update_payload/update_metadata_pb2.py
index 46c475e..8cf87e3 100644
--- a/scripts/update_payload/update_metadata_pb2.py
+++ b/scripts/update_payload/update_metadata_pb2.py
@@ -13,7 +13,7 @@
 DESCRIPTOR = _descriptor.FileDescriptor(
   name='update_metadata.proto',
   package='chromeos_update_engine',
-  serialized_pb='\n\x15update_metadata.proto\x12\x16\x63hromeos_update_engine\"1\n\x06\x45xtent\x12\x13\n\x0bstart_block\x18\x01 \x01(\x04\x12\x12\n\nnum_blocks\x18\x02 \x01(\x04\"z\n\nSignatures\x12@\n\nsignatures\x18\x01 \x03(\x0b\x32,.chromeos_update_engine.Signatures.Signature\x1a*\n\tSignature\x12\x0f\n\x07version\x18\x01 \x01(\r\x12\x0c\n\x04\x64\x61ta\x18\x02 \x01(\x0c\"+\n\rPartitionInfo\x12\x0c\n\x04size\x18\x01 \x01(\x04\x12\x0c\n\x04hash\x18\x02 \x01(\x0c\"w\n\tImageInfo\x12\r\n\x05\x62oard\x18\x01 \x01(\t\x12\x0b\n\x03key\x18\x02 \x01(\t\x12\x0f\n\x07\x63hannel\x18\x03 \x01(\t\x12\x0f\n\x07version\x18\x04 \x01(\t\x12\x15\n\rbuild_channel\x18\x05 \x01(\t\x12\x15\n\rbuild_version\x18\x06 \x01(\t\"\xd2\x03\n\x10InstallOperation\x12;\n\x04type\x18\x01 \x02(\x0e\x32-.chromeos_update_engine.InstallOperation.Type\x12\x13\n\x0b\x64\x61ta_offset\x18\x02 \x01(\r\x12\x13\n\x0b\x64\x61ta_length\x18\x03 \x01(\r\x12\x33\n\x0bsrc_extents\x18\x04 \x03(\x0b\x32\x1e.chromeos_update_engine.Extent\x12\x12\n\nsrc_length\x18\x05 \x01(\x04\x12\x33\n\x0b\x64st_extents\x18\x06 \x03(\x0b\x32\x1e.chromeos_update_engine.Extent\x12\x12\n\ndst_length\x18\x07 \x01(\x04\x12\x18\n\x10\x64\x61ta_sha256_hash\x18\x08 \x01(\x0c\x12\x17\n\x0fsrc_sha256_hash\x18\t \x01(\x0c\"\x91\x01\n\x04Type\x12\x0b\n\x07REPLACE\x10\x00\x12\x0e\n\nREPLACE_BZ\x10\x01\x12\x08\n\x04MOVE\x10\x02\x12\n\n\x06\x42SDIFF\x10\x03\x12\x0f\n\x0bSOURCE_COPY\x10\x04\x12\x11\n\rSOURCE_BSDIFF\x10\x05\x12\x08\n\x04ZERO\x10\x06\x12\x0b\n\x07\x44ISCARD\x10\x07\x12\x0e\n\nREPLACE_XZ\x10\x08\x12\x0b\n\x07IMGDIFF\x10\t\"\x88\x03\n\x0fPartitionUpdate\x12\x16\n\x0epartition_name\x18\x01 \x02(\t\x12\x17\n\x0frun_postinstall\x18\x02 \x01(\x08\x12\x18\n\x10postinstall_path\x18\x03 \x01(\t\x12\x17\n\x0f\x66ilesystem_type\x18\x04 \x01(\t\x12M\n\x17new_partition_signature\x18\x05 \x03(\x0b\x32,.chromeos_update_engine.Signatures.Signature\x12\x41\n\x12old_partition_info\x18\x06 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfo\x12\x41\n\x12new_partition_info\x18\x07 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfo\x12<\n\noperations\x18\x08 \x03(\x0b\x32(.chromeos_update_engine.InstallOperation\"\xc4\x05\n\x14\x44\x65ltaArchiveManifest\x12\x44\n\x12install_operations\x18\x01 \x03(\x0b\x32(.chromeos_update_engine.InstallOperation\x12K\n\x19kernel_install_operations\x18\x02 \x03(\x0b\x32(.chromeos_update_engine.InstallOperation\x12\x18\n\nblock_size\x18\x03 \x01(\r:\x04\x34\x30\x39\x36\x12\x19\n\x11signatures_offset\x18\x04 \x01(\x04\x12\x17\n\x0fsignatures_size\x18\x05 \x01(\x04\x12>\n\x0fold_kernel_info\x18\x06 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfo\x12>\n\x0fnew_kernel_info\x18\x07 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfo\x12>\n\x0fold_rootfs_info\x18\x08 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfo\x12>\n\x0fnew_rootfs_info\x18\t \x01(\x0b\x32%.chromeos_update_engine.PartitionInfo\x12\x39\n\x0eold_image_info\x18\n \x01(\x0b\x32!.chromeos_update_engine.ImageInfo\x12\x39\n\x0enew_image_info\x18\x0b \x01(\x0b\x32!.chromeos_update_engine.ImageInfo\x12\x18\n\rminor_version\x18\x0c \x01(\r:\x01\x30\x12;\n\npartitions\x18\r \x03(\x0b\x32\'.chromeos_update_engine.PartitionUpdateB\x02H\x03')
+  serialized_pb='\n\x15update_metadata.proto\x12\x16\x63hromeos_update_engine\"1\n\x06\x45xtent\x12\x13\n\x0bstart_block\x18\x01 \x01(\x04\x12\x12\n\nnum_blocks\x18\x02 \x01(\x04\"z\n\nSignatures\x12@\n\nsignatures\x18\x01 \x03(\x0b\x32,.chromeos_update_engine.Signatures.Signature\x1a*\n\tSignature\x12\x0f\n\x07version\x18\x01 \x01(\r\x12\x0c\n\x04\x64\x61ta\x18\x02 \x01(\x0c\"+\n\rPartitionInfo\x12\x0c\n\x04size\x18\x01 \x01(\x04\x12\x0c\n\x04hash\x18\x02 \x01(\x0c\"w\n\tImageInfo\x12\r\n\x05\x62oard\x18\x01 \x01(\t\x12\x0b\n\x03key\x18\x02 \x01(\t\x12\x0f\n\x07\x63hannel\x18\x03 \x01(\t\x12\x0f\n\x07version\x18\x04 \x01(\t\x12\x15\n\rbuild_channel\x18\x05 \x01(\t\x12\x15\n\rbuild_version\x18\x06 \x01(\t\"\xd3\x03\n\x10InstallOperation\x12;\n\x04type\x18\x01 \x02(\x0e\x32-.chromeos_update_engine.InstallOperation.Type\x12\x13\n\x0b\x64\x61ta_offset\x18\x02 \x01(\r\x12\x13\n\x0b\x64\x61ta_length\x18\x03 \x01(\r\x12\x33\n\x0bsrc_extents\x18\x04 \x03(\x0b\x32\x1e.chromeos_update_engine.Extent\x12\x12\n\nsrc_length\x18\x05 \x01(\x04\x12\x33\n\x0b\x64st_extents\x18\x06 \x03(\x0b\x32\x1e.chromeos_update_engine.Extent\x12\x12\n\ndst_length\x18\x07 \x01(\x04\x12\x18\n\x10\x64\x61ta_sha256_hash\x18\x08 \x01(\x0c\x12\x17\n\x0fsrc_sha256_hash\x18\t \x01(\x0c\"\x92\x01\n\x04Type\x12\x0b\n\x07REPLACE\x10\x00\x12\x0e\n\nREPLACE_BZ\x10\x01\x12\x08\n\x04MOVE\x10\x02\x12\n\n\x06\x42SDIFF\x10\x03\x12\x0f\n\x0bSOURCE_COPY\x10\x04\x12\x11\n\rSOURCE_BSDIFF\x10\x05\x12\x08\n\x04ZERO\x10\x06\x12\x0b\n\x07\x44ISCARD\x10\x07\x12\x0e\n\nREPLACE_XZ\x10\x08\x12\x0c\n\x08PUFFDIFF\x10\t\"\xa6\x03\n\x0fPartitionUpdate\x12\x16\n\x0epartition_name\x18\x01 \x02(\t\x12\x17\n\x0frun_postinstall\x18\x02 \x01(\x08\x12\x18\n\x10postinstall_path\x18\x03 \x01(\t\x12\x17\n\x0f\x66ilesystem_type\x18\x04 \x01(\t\x12M\n\x17new_partition_signature\x18\x05 \x03(\x0b\x32,.chromeos_update_engine.Signatures.Signature\x12\x41\n\x12old_partition_info\x18\x06 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfo\x12\x41\n\x12new_partition_info\x18\x07 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfo\x12<\n\noperations\x18\x08 \x03(\x0b\x32(.chromeos_update_engine.InstallOperation\x12\x1c\n\x14postinstall_optional\x18\t \x01(\x08\"\xc4\x05\n\x14\x44\x65ltaArchiveManifest\x12\x44\n\x12install_operations\x18\x01 \x03(\x0b\x32(.chromeos_update_engine.InstallOperation\x12K\n\x19kernel_install_operations\x18\x02 \x03(\x0b\x32(.chromeos_update_engine.InstallOperation\x12\x18\n\nblock_size\x18\x03 \x01(\r:\x04\x34\x30\x39\x36\x12\x19\n\x11signatures_offset\x18\x04 \x01(\x04\x12\x17\n\x0fsignatures_size\x18\x05 \x01(\x04\x12>\n\x0fold_kernel_info\x18\x06 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfo\x12>\n\x0fnew_kernel_info\x18\x07 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfo\x12>\n\x0fold_rootfs_info\x18\x08 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfo\x12>\n\x0fnew_rootfs_info\x18\t \x01(\x0b\x32%.chromeos_update_engine.PartitionInfo\x12\x39\n\x0eold_image_info\x18\n \x01(\x0b\x32!.chromeos_update_engine.ImageInfo\x12\x39\n\x0enew_image_info\x18\x0b \x01(\x0b\x32!.chromeos_update_engine.ImageInfo\x12\x18\n\rminor_version\x18\x0c \x01(\r:\x01\x30\x12;\n\npartitions\x18\r \x03(\x0b\x32\'.chromeos_update_engine.PartitionUpdateB\x02H\x03')
 
 
 
@@ -60,14 +60,14 @@
       options=None,
       type=None),
     _descriptor.EnumValueDescriptor(
-      name='IMGDIFF', index=9, number=9,
+      name='PUFFDIFF', index=9, number=9,
       options=None,
       type=None),
   ],
   containing_type=None,
   options=None,
   serialized_start=712,
-  serialized_end=857,
+  serialized_end=858,
 )
 
 
@@ -347,7 +347,7 @@
   is_extendable=False,
   extension_ranges=[],
   serialized_start=391,
-  serialized_end=857,
+  serialized_end=858,
 )
 
 
@@ -414,6 +414,13 @@
       message_type=None, enum_type=None, containing_type=None,
       is_extension=False, extension_scope=None,
       options=None),
+    _descriptor.FieldDescriptor(
+      name='postinstall_optional', full_name='chromeos_update_engine.PartitionUpdate.postinstall_optional', index=8,
+      number=9, type=8, cpp_type=7, label=1,
+      has_default_value=False, default_value=False,
+      message_type=None, enum_type=None, containing_type=None,
+      is_extension=False, extension_scope=None,
+      options=None),
   ],
   extensions=[
   ],
@@ -423,8 +430,8 @@
   options=None,
   is_extendable=False,
   extension_ranges=[],
-  serialized_start=860,
-  serialized_end=1252,
+  serialized_start=861,
+  serialized_end=1283,
 )
 
 
@@ -535,8 +542,8 @@
   options=None,
   is_extendable=False,
   extension_ranges=[],
-  serialized_start=1255,
-  serialized_end=1963,
+  serialized_start=1286,
+  serialized_end=1994,
 )
 
 _SIGNATURES_SIGNATURE.containing_type = _SIGNATURES;