diff --git a/avb/avbtool b/avb/avbtool
index b742466..2830e20 100755
--- a/avb/avbtool
+++ b/avb/avbtool
@@ -2142,7 +2142,8 @@ class Avb(object):
         expected_chain_partitions_map[partition_name] = (rollback_index_location, pk_blob)
 
     image_dir = os.path.dirname(image_filename)
-    image_ext = os.path.splitext(image_filename)[1]
+    #image_ext = os.path.splitext(image_filename)[1]
+    image_ext = image_filename[image_filename.index('.'):]
 
     key_blob = None
     if key_path: