diff --git a/payload_generator/annotated_operation.cc b/payload_generator/annotated_operation.cc
index 70350ed..3f28c8d 100644
--- a/payload_generator/annotated_operation.cc
+++ b/payload_generator/annotated_operation.cc
@@ -39,11 +39,10 @@
 
 bool AnnotatedOperation::SetOperationBlob(chromeos::Blob* blob,
                                           BlobFileWriter* blob_file) {
-  op.set_data_length(blob->size());
   off_t data_offset = blob_file->StoreBlob(*blob);
-  if (data_offset == -1)
-    return false;
+  TEST_AND_RETURN_FALSE(data_offset != -1);
   op.set_data_offset(data_offset);
+  op.set_data_length(blob->size());
   return true;
 }
 
diff --git a/payload_generator/full_update_generator.cc b/payload_generator/full_update_generator.cc
index 1348422..a627823 100644
--- a/payload_generator/full_update_generator.cc
+++ b/payload_generator/full_update_generator.cc
@@ -112,10 +112,7 @@
     op_type = InstallOperation::REPLACE;
   }
 
-  off_t op_offset = blob_file_->StoreBlob(op_blob);
-  TEST_AND_RETURN_FALSE(op_offset >= 0);
-  aop_->op.set_data_offset(op_offset);
-  aop_->op.set_data_length(op_blob.size());
+  TEST_AND_RETURN_FALSE(aop_->SetOperationBlob(&op_blob, blob_file_));
   aop_->op.set_type(op_type);
   return true;
 }