diff --git a/scripts/update_payload/checker.py b/scripts/update_payload/checker.py
index 48b18e6..f2aa7bb 100644
--- a/scripts/update_payload/checker.py
+++ b/scripts/update_payload/checker.py
@@ -778,6 +778,14 @@
         dst_idx = dst_extent.start_block
         dst_num = dst_extent.num_blocks
 
+      # Check: start block is not 0. See crbug/480751; there are still versions
+      # of update_engine which fail when seeking to 0 in PReadAll and PWriteAll,
+      # so we need to fail payloads that try to MOVE to/from block 0.
+      if src_idx == 0 or dst_idx == 0:
+        raise error.PayloadError(
+            '%s: MOVE operation cannot have extent with start block 0' %
+            op_name)
+
       if self.check_move_same_src_dst_block and src_idx == dst_idx:
         raise error.PayloadError(
             '%s: src/dst block number %d is the same (%d).' %
diff --git a/scripts/update_payload/checker_unittest.py b/scripts/update_payload/checker_unittest.py
index eb8b564..b57c2fc 100755
--- a/scripts/update_payload/checker_unittest.py
+++ b/scripts/update_payload/checker_unittest.py
@@ -633,7 +633,7 @@
     op.type = common.OpType.MOVE
 
     self.AddToMessage(op.src_extents,
-                      self.NewExtentList((0, 4), (12, 2), (1024, 128)))
+                      self.NewExtentList((1, 4), (12, 2), (1024, 128)))
     self.AddToMessage(op.dst_extents,
                       self.NewExtentList((16, 128), (512, 6)))
     self.assertIsNone(
@@ -646,7 +646,7 @@
     op.type = common.OpType.MOVE
 
     self.AddToMessage(op.src_extents,
-                      self.NewExtentList((0, 4), (12, 2), (1024, 128)))
+                      self.NewExtentList((1, 4), (12, 2), (1024, 128)))
     self.AddToMessage(op.dst_extents,
                       self.NewExtentList((16, 128), (512, 6)))
     self.assertRaises(
@@ -661,7 +661,7 @@
     op.type = common.OpType.MOVE
 
     self.AddToMessage(op.src_extents,
-                      self.NewExtentList((0, 4), (12, 2), (1024, 127)))
+                      self.NewExtentList((1, 4), (12, 2), (1024, 127)))
     self.AddToMessage(op.dst_extents,
                       self.NewExtentList((16, 128), (512, 6)))
     self.assertRaises(
@@ -676,7 +676,7 @@
     op.type = common.OpType.MOVE
 
     self.AddToMessage(op.src_extents,
-                      self.NewExtentList((0, 4), (12, 2), (1024, 128)))
+                      self.NewExtentList((1, 4), (12, 2), (1024, 128)))
     self.AddToMessage(op.dst_extents,
                       self.NewExtentList((16, 128), (512, 5)))
     self.assertRaises(
@@ -691,7 +691,7 @@
     op.type = common.OpType.MOVE
 
     self.AddToMessage(op.src_extents,
-                      self.NewExtentList((0, 4), (12, 2), (1024, 128)))
+                      self.NewExtentList((1, 4), (12, 2), (1024, 128)))
     self.AddToMessage(op.dst_extents,
                       self.NewExtentList((16, 128), (512, 5)))
     self.assertRaises(
@@ -699,7 +699,7 @@
         payload_checker._CheckMoveOperation,
         op, None, 134, 134, 'foo')
     self.AddToMessage(op.src_extents,
-                      self.NewExtentList((0, 4), (12, 2), (1024, 129)))
+                      self.NewExtentList((1, 4), (12, 2), (1024, 129)))
     self.AddToMessage(op.dst_extents,
                       self.NewExtentList((16, 128), (512, 6)))
     self.assertRaises(
@@ -714,7 +714,7 @@
     op.type = common.OpType.MOVE
 
     self.AddToMessage(op.src_extents,
-                      self.NewExtentList((0, 4), (12, 2), (1024, 128)))
+                      self.NewExtentList((1, 4), (12, 2), (1024, 128)))
     self.AddToMessage(op.dst_extents,
                       self.NewExtentList((16, 128), (512, 7)))
     self.assertRaises(
@@ -729,6 +729,21 @@
     op.type = common.OpType.MOVE
 
     self.AddToMessage(op.src_extents,
+                      self.NewExtentList((1, 4), (12, 2), (1024, 128)))
+    self.AddToMessage(op.dst_extents,
+                      self.NewExtentList((8, 128), (512, 6)))
+    self.assertRaises(
+        update_payload.PayloadError,
+        payload_checker._CheckMoveOperation,
+        op, None, 134, 134, 'foo')
+
+  def testCheckMoveOperation_FailZeroStartBlock(self):
+    """Tests _CheckMoveOperation(); fails, has extent with start block 0."""
+    payload_checker = checker.PayloadChecker(self.MockPayload())
+    op = update_metadata_pb2.DeltaArchiveManifest.InstallOperation()
+    op.type = common.OpType.MOVE
+
+    self.AddToMessage(op.src_extents,
                       self.NewExtentList((0, 4), (12, 2), (1024, 128)))
     self.AddToMessage(op.dst_extents,
                       self.NewExtentList((8, 128), (512, 6)))
@@ -737,6 +752,15 @@
         payload_checker._CheckMoveOperation,
         op, None, 134, 134, 'foo')
 
+    self.AddToMessage(op.src_extents,
+                      self.NewExtentList((1, 4), (12, 2), (1024, 128)))
+    self.AddToMessage(op.dst_extents,
+                      self.NewExtentList((0, 128), (512, 6)))
+    self.assertRaises(
+        update_payload.PayloadError,
+        payload_checker._CheckMoveOperation,
+        op, None, 134, 134, 'foo')
+
   def testCheckBsdiff(self):
     """Tests _CheckMoveOperation()."""
     payload_checker = checker.PayloadChecker(self.MockPayload())
@@ -829,10 +853,10 @@
                    common.OpType.SOURCE_COPY, common.OpType.SOURCE_BSDIFF):
       if fail_src_extents:
         self.AddToMessage(op.src_extents,
-                          self.NewExtentList((0, 0)))
+                          self.NewExtentList((1, 0)))
       else:
         self.AddToMessage(op.src_extents,
-                          self.NewExtentList((0, 16)))
+                          self.NewExtentList((1, 16)))
         total_src_blocks = 16
 
     if op_type in (common.OpType.REPLACE, common.OpType.REPLACE_BZ):