diff --git a/src/calibre/ebooks/metadata/book/__init__.py b/src/calibre/ebooks/metadata/book/__init__.py
index e7f58ce858..84a88606f2 100644
--- a/src/calibre/ebooks/metadata/book/__init__.py
+++ b/src/calibre/ebooks/metadata/book/__init__.py
@@ -110,7 +110,7 @@ COPYABLE_METADATA_FIELDS = SOCIAL_METADATA_FIELDS.union(
                            frozenset(['title', 'title_sort', 'authors',
                                       'author_sort', 'author_sort_map' 'comments',
                                       'cover_data', 'tags', 'language', 'lpath',
-                                      'size'])
+                                      'size', 'thumbnail'])
 
 SERIALIZABLE_FIELDS =      SOCIAL_METADATA_FIELDS.union(
                            USER_METADATA_FIELDS).union(
diff --git a/src/calibre/ebooks/metadata/book/base.py b/src/calibre/ebooks/metadata/book/base.py
index f2031afd0e..7812f81180 100644
--- a/src/calibre/ebooks/metadata/book/base.py
+++ b/src/calibre/ebooks/metadata/book/base.py
@@ -223,7 +223,7 @@ class Metadata(object):
                 self.author_sort = other.author_sort
 
         if replace_metadata:
-            SPECIAL_FIELDS = frozenset(['lpath', 'size', 'comments'])
+            SPECIAL_FIELDS = frozenset(['lpath', 'size', 'comments', 'thumbnail'])
             for attr in COPYABLE_METADATA_FIELDS:
                 setattr(self, attr, getattr(other, attr, 1.0 if \
                         attr == 'series_index' else None))
@@ -238,6 +238,7 @@ class Metadata(object):
             for attr in COPYABLE_METADATA_FIELDS:
                 if hasattr(other, attr):
                     copy_not_none(self, other, attr)
+            copy_not_none(self, other, 'thumbnail')
             if other.tags:
                 # Case-insensitive but case preserving merging
                 lotags = [t.lower() for t in other.tags]
diff --git a/src/calibre/ebooks/metadata/book/json_codec.py b/src/calibre/ebooks/metadata/book/json_codec.py
index ea0de07342..51b9722803 100644
--- a/src/calibre/ebooks/metadata/book/json_codec.py
+++ b/src/calibre/ebooks/metadata/book/json_codec.py
@@ -12,6 +12,7 @@ from calibre.ebooks.metadata.book import SERIALIZABLE_FIELDS
 from calibre.constants import filesystem_encoding, preferred_encoding
 from calibre.library.field_metadata import FieldMetadata
 from calibre.utils.date import parse_date, isoformat, UNDEFINED_DATE
+from calibre.utils.magick import Image
 from calibre import isbytestring
 
 # Translate datetimes to and from strings. The string form is the datetime in
@@ -32,6 +33,14 @@ def encode_thumbnail(thumbnail):
     '''
     if thumbnail is None:
         return None
+    if not isinstance(thumbnail, tuple):
+        try:
+            img = Image()
+            img.load(thumbnail)
+            width, height = img.size
+            thumbnail = (width, height, thumbnail)
+        except:
+            return None
     return (thumbnail[0], thumbnail[1], b64encode(str(thumbnail[2])))
 
 def decode_thumbnail(tup):
diff --git a/src/calibre/gui2/library/models.py b/src/calibre/gui2/library/models.py
index b81628cd27..4e8e9a10bd 100644
--- a/src/calibre/gui2/library/models.py
+++ b/src/calibre/gui2/library/models.py
@@ -1056,7 +1056,10 @@ class DeviceBooksModel(BooksModel): # {{{
             if hasattr(cdata, 'image_path'):
                 img.load(cdata.image_path)
             elif cdata:
-                img.loadFromData(cdata)
+                if isinstance(cdata, tuple):
+                    img.loadFromData(cdata[2])
+                else:
+                    img.loadFromData(cdata)
             if img.isNull():
                 img = self.default_image
             data['cover'] = img