diff --git a/odoo/tools/image.py b/odoo/tools/image.py
index 4341e11a571..0ec27ff445c 100644
--- a/odoo/tools/image.py
+++ b/odoo/tools/image.py
@@ -199,11 +199,9 @@ def crop_image(data, type='top', ratio=False, size=None, image_format="PNG"):
         raise ValueError('ERROR: invalid value for crop_type')
     if size:
         thumbnail = Image.open(io.BytesIO(output_stream.getvalue()))
-        output_stream.truncate(0)
-        output_stream.seek(0)  # for python 3
         thumbnail.thumbnail(size, Image.ANTIALIAS)
         thumbnail.save(output_stream, image_format)
-    return output_stream.getvalue().encode('base64')
+    return base64.b64encode(output_stream.getvalue())
 
 # ----------------------------------------
 # Colors