diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 95aeb62..403c67d 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -30,7 +30,6 @@
 import zipfile
 
 import blockimgdiff
-import rangelib
 
 from hashlib import sha1 as sha1
 
@@ -1255,6 +1254,7 @@
     OPTIONS.tempfiles.append(tmpdir)
     self.path = os.path.join(tmpdir, partition)
     b.Compute(self.path)
+    self._required_cache = b.max_stashed_size
 
     if src is None:
       _, self.device = GetTypeAndDevice("/" + partition, OPTIONS.info_dict)
@@ -1262,6 +1262,10 @@
       _, self.device = GetTypeAndDevice("/" + partition,
                                         OPTIONS.source_info_dict)
 
+  @property
+  def required_cache(self):
+    return self._required_cache
+
   def WriteScript(self, script, output_zip, progress=None):
     if not self.src:
       # write the output unconditionally