diff --git a/tools/releasetools/ota_from_target_files b/tools/releasetools/ota_from_target_files
index 6e0fefc..b71baf9 100755
--- a/tools/releasetools/ota_from_target_files
+++ b/tools/releasetools/ota_from_target_files
@@ -349,8 +349,9 @@
   partition = itemset.partition
 
   for info in input_zip.infolist():
-    if info.filename.startswith(partition.upper() + "/"):
-      basefilename = info.filename[7:]
+    prefix = partition.upper() + "/"
+    if info.filename.startswith(prefix):
+      basefilename = info.filename[len(prefix):]
       if IsSymlink(info):
         symlinks.append((input_zip.read(info.filename),
                          "/" + partition + "/" + basefilename))
@@ -663,7 +664,7 @@
   prefix = partition.upper() + "/"
   for info in z.infolist():
     if info.filename.startswith(prefix) and not IsSymlink(info):
-      basefilename = info.filename[7:]
+      basefilename = info.filename[len(prefix):]
       fn = partition + "/" + basefilename
       data = z.read(info.filename)
       out[fn] = common.File(fn, data)