diff --git a/legendary/models/chunk.py b/legendary/models/chunk.py
index 7cdd2db..3941b68 100644
--- a/legendary/models/chunk.py
+++ b/legendary/models/chunk.py
@@ -147,3 +147,5 @@ class Chunk:
 
         if not fp:
             return bio.getvalue()
+        else:
+            return bio.tell()
diff --git a/legendary/models/manifest.py b/legendary/models/manifest.py
index 30a9f02..b264d61 100644
--- a/legendary/models/manifest.py
+++ b/legendary/models/manifest.py
@@ -168,6 +168,8 @@ class Manifest:
 
         if not fp:
             return bio.getvalue()
+        else:
+            return bio.tell()
 
 
 class ManifestMeta: