diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index fe63458..4c452ad 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -827,10 +827,10 @@
     ranges = image.file_map[entry]
 
     # If a RangeSet has been tagged as using shared blocks while loading the
-    # image, its block list must be already incomplete due to that reason. Don't
-    # give it 'incomplete' tag to avoid messing up the imgdiff stats.
+    # image, check the original block list to determine its completeness. Note
+    # that the 'incomplete' flag would be tagged to the original RangeSet only.
     if ranges.extra.get('uses_shared_blocks'):
-      continue
+      ranges = ranges.extra['uses_shared_blocks']
 
     if RoundUpTo4K(info.file_size) > ranges.size() * 4096:
       ranges.extra['incomplete'] = True