diff --git a/src/calibre/ebooks/metadata/__init__.py b/src/calibre/ebooks/metadata/__init__.py
index 690cca511a..4d126fda9d 100644
--- a/src/calibre/ebooks/metadata/__init__.py
+++ b/src/calibre/ebooks/metadata/__init__.py
@@ -282,7 +282,7 @@ class MetaInformation(object):
         for attr in ('author_sort', 'title_sort', 'category',
                      'publisher', 'series', 'series_index', 'rating',
                      'isbn', 'application_id', 'manifest', 'spine', 'toc',
-                     'cover', 'language', 'guide', 'book_producer',
+                     'cover', 'guide', 'book_producer',
                      'timestamp', 'lccn', 'lcc', 'ddc', 'pubdate', 'rights',
                      'publication_type', 'uuid'):
             if hasattr(mi, attr):
@@ -314,6 +314,11 @@ class MetaInformation(object):
         if len(other_comments.strip()) > len(my_comments.strip()):
             self.comments = other_comments
 
+        other_lang = getattr(mi, 'language', None)
+        if other_lang and other_lang.lower() != 'und':
+            self.language = other_lang
+
+
     def format_series_index(self):
         try:
             x = float(self.series_index)
diff --git a/src/calibre/ebooks/metadata/opf2.py b/src/calibre/ebooks/metadata/opf2.py
index 46924cad1f..579398d3b0 100644
--- a/src/calibre/ebooks/metadata/opf2.py
+++ b/src/calibre/ebooks/metadata/opf2.py
@@ -18,7 +18,7 @@ from calibre.constants import __appname__, __version__, filesystem_encoding
 from calibre.ebooks.metadata.toc import TOC
 from calibre.ebooks.metadata import MetaInformation, string_to_authors
 from calibre.utils.date import parse_date, isoformat
-
+from calibre.utils.localization import get_lang
 
 class Resource(object):
     '''
@@ -1069,7 +1069,7 @@ class OPFCreator(MetaInformation):
             dc_attrs={'id':__appname__+'_id'}))
         if getattr(self, 'pubdate', None) is not None:
             a(DC_ELEM('date', self.pubdate.isoformat()))
-        a(DC_ELEM('language', self.language if self.language else 'UND'))
+        a(DC_ELEM('language', self.language if self.language else get_lang()))
         if self.comments:
             a(DC_ELEM('description', self.comments))
         if self.publisher:
@@ -1184,7 +1184,6 @@ def metadata_to_opf(mi, as_string=True):
     factory(DC('contributor'), mi.book_producer, __appname__, 'bkp')
     if hasattr(mi.pubdate, 'isoformat'):
         factory(DC('date'), isoformat(mi.pubdate))
-    factory(DC('language'), mi.language)
     if mi.category:
         factory(DC('type'), mi.category)
     if mi.comments:
@@ -1195,6 +1194,7 @@ def metadata_to_opf(mi, as_string=True):
         factory(DC('identifier'), mi.isbn, scheme='ISBN')
     if mi.rights:
         factory(DC('rights'), mi.rights)
+    factory(DC('language'), mi.language if mi.language and mi.language.lower() != 'und' else get_lang())
     if mi.tags:
         for tag in mi.tags:
             factory(DC('subject'), tag)