diff --git a/delta_diff_generator.cc b/delta_diff_generator.cc
index 48fe177..2df0de9 100644
--- a/delta_diff_generator.cc
+++ b/delta_diff_generator.cc
@@ -1405,7 +1405,7 @@
     LOG_IF(WARNING, old_image_block_count != new_image_block_count)
         << "Old and new images have different block counts.";
 
-    // If new_image_info is present, old_image_info must but be present.
+    // If new_image_info is present, old_image_info must be present.
     TEST_AND_RETURN_FALSE((bool)old_image_info == (bool)new_image_info);
   } else {
     // old_image_info must not be present for a full update.
diff --git a/generate_delta_main.cc b/generate_delta_main.cc
index d7de1ab..ede8ab9 100644
--- a/generate_delta_main.cc
+++ b/generate_delta_main.cc
@@ -332,7 +332,7 @@
   ImageInfo old_image_info;
   ImageInfo new_image_info;
 
-  // TODO(dgarrett) Check the result is True when these args are required.
+  // Ignore failures. These are optional arguments.
   ParseImageInfo(FLAGS_new_channel,
                  FLAGS_new_board,
                  FLAGS_new_version,
@@ -341,14 +341,14 @@
                  FLAGS_new_build_version,
                  &new_image_info);
 
-  CHECK(is_delta || !ParseImageInfo(FLAGS_old_channel,
-                                    FLAGS_old_board,
-                                    FLAGS_old_version,
-                                    FLAGS_old_key,
-                                    FLAGS_old_build_channel,
-                                    FLAGS_old_build_version,
-                                    &old_image_info));
-
+  // Ignore failures. These are optional arguments.
+  ParseImageInfo(FLAGS_old_channel,
+                 FLAGS_old_board,
+                 FLAGS_old_version,
+                 FLAGS_old_key,
+                 FLAGS_old_build_channel,
+                 FLAGS_old_build_version,
+                 &old_image_info);
 
   if (is_delta) {
     LOG(INFO) << "Generating delta update";