diff --git a/tools/releasetools/blockimgdiff.py b/tools/releasetools/blockimgdiff.py
index 544b1d0..0a387ec 100644
--- a/tools/releasetools/blockimgdiff.py
+++ b/tools/releasetools/blockimgdiff.py
@@ -82,6 +82,7 @@
   """A zero-length image."""
   blocksize = 4096
   care_map = RangeSet()
+  clobbered_blocks = RangeSet()
   total_blocks = 0
   file_map = {}
   def ReadRangeSet(self, ranges):
@@ -114,6 +115,7 @@
 
     self.total_blocks = len(self.data) / self.blocksize
     self.care_map = RangeSet(data=(0, self.total_blocks))
+    self.clobbered_blocks = RangeSet()
 
     zero_blocks = []
     nonzero_blocks = []
@@ -135,6 +137,8 @@
     return [self.data[s*self.blocksize:e*self.blocksize] for (s, e) in ranges]
 
   def TotalSha1(self):
+    # DataImage always carries empty clobbered_blocks.
+    assert self.clobbered_blocks.size() == 0
     return sha1(self.data).hexdigest()
 
 
@@ -184,6 +188,10 @@
 #      (Typically a domain is a file, and the key in file_map is the
 #      pathname.)
 #
+#    clobbered_blocks: a RangeSet containing which blocks contain data
+#      but may be altered by the FS. They need to be excluded when
+#      verifying the partition integrity.
+#
 #    ReadRangeSet(): a function that takes a RangeSet and returns the
 #      data contained in the image blocks of that RangeSet.  The data
 #      is returned as a list or tuple of strings; concatenating the
@@ -193,7 +201,7 @@
 #
 #    TotalSha1(): a function that returns (as a hex string) the SHA-1
 #      hash of all the data in the image (ie, all the blocks in the
-#      care_map)
+#      care_map minus clobbered_blocks).
 #
 # When creating a BlockImageDiff, the src image may be None, in which
 # case the list of transfers produced will never read from the
@@ -844,6 +852,12 @@
                  "zero", self.transfers)
         continue
 
+      elif tgt_fn == "__COPY":
+        # "__COPY" domain includes all the blocks not contained in any
+        # file and that need to be copied unconditionally to the target.
+        Transfer(tgt_fn, None, tgt_ranges, empty, "new", self.transfers)
+        continue
+
       elif tgt_fn in self.src.file_map:
         # Look for an exact pathname match in the source.
         Transfer(tgt_fn, tgt_fn, tgt_ranges, self.src.file_map[tgt_fn],