diff --git a/payload_consumer/xor_extent_writer.h b/payload_consumer/xor_extent_writer.h
index ea270bc..d965aba 100644
--- a/payload_consumer/xor_extent_writer.h
+++ b/payload_consumer/xor_extent_writer.h
@@ -36,7 +36,7 @@
                   FileDescriptorPtr source_fd,
                   android::snapshot::ICowWriter* cow_writer,
                   const ExtentMap<const CowMergeOperation*>& xor_map,
-                  size_t partition_size)
+                  uint64_t partition_size)
       : src_extents_(op.src_extents()),
         source_fd_(source_fd),
         xor_map_(xor_map),