diff --git a/src/calibre/ebooks/mobi/writer.py b/src/calibre/ebooks/mobi/writer.py
index 11391c56b5..94df4b6998 100644
--- a/src/calibre/ebooks/mobi/writer.py
+++ b/src/calibre/ebooks/mobi/writer.py
@@ -120,11 +120,11 @@ class Serializer(object):
             if hrefs[path].media_type not in OEB_DOCS:
                 continue
             buffer.write('<reference type="')
-            self.serialize_text(ref.type)
+            self.serialize_text(ref.type, quot=True)
             buffer.write('" ')
             if ref.title is not None:
                 buffer.write('title="')
-                self.serialize_text(ref.title)
+                self.serialize_text(ref.title, quot=True)
                 buffer.write('" ')
             self.serialize_href(ref.href)
             # Space required or won't work, I kid you not
diff --git a/src/calibre/ebooks/oeb/base.py b/src/calibre/ebooks/oeb/base.py
index 2c171f3490..4248657e23 100644
--- a/src/calibre/ebooks/oeb/base.py
+++ b/src/calibre/ebooks/oeb/base.py
@@ -551,7 +551,7 @@ class Guide(object):
         TYPES = set(t for t, _ in _TYPES_TITLES)
         TITLES = dict(_TYPES_TITLES)
         ORDER = dict((t, i) for (t, _), i in izip(_TYPES_TITLES, count(0)))
-    
+        
         def __init__(self, type, title, href):
             if type.lower() in self.TYPES:
                 type = type.lower()