diff --git a/src/jp2.py b/src/jp2.py
index 44d3e21..95014cb 100644
--- a/src/jp2.py
+++ b/src/jp2.py
@@ -73,6 +73,7 @@ def parse_res(data):
         if boxType == b"resc":
             hdpi, vdpi = parse_resc(boxContents)
             break
+        byteStart = byteEnd
     return hdpi, vdpi