diff --git a/src/calibre/ebooks/mobi/reader.py b/src/calibre/ebooks/mobi/reader.py
index d9c6853795..3d858864a8 100644
--- a/src/calibre/ebooks/mobi/reader.py
+++ b/src/calibre/ebooks/mobi/reader.py
@@ -253,6 +253,8 @@ class MobiReader(object):
 
                 .italic { font-style: italic }
 
+                .underline { text-decoration: underline }
+
                 .mbp_pagebreak {
                     page-break-after: always; margin: 0; display: block
                 }
@@ -601,6 +603,9 @@ class MobiReader(object):
             elif tag.tag == 'i':
                 tag.tag = 'span'
                 tag.attrib['class'] = 'italic'
+            elif tag.tag == 'u':
+                tag.tag = 'span'
+                tag.attrib['class'] = 'underline'
             elif tag.tag == 'b':
                 tag.tag = 'span'
                 tag.attrib['class'] = 'bold'
diff --git a/src/calibre/ebooks/oeb/base.py b/src/calibre/ebooks/oeb/base.py
index 1f71e32548..db83fca496 100644
--- a/src/calibre/ebooks/oeb/base.py
+++ b/src/calibre/ebooks/oeb/base.py
@@ -1049,8 +1049,8 @@ class Manifest(object):
 
             # Remove hyperlinks with no content as they cause rendering
             # artifacts in browser based renderers
-            # Also remove empty <b> and <i> tags
-            for a in xpath(data, '//h:a[@href]|//h:i|//h:b'):
+            # Also remove empty <b>, <u> and <i> tags
+            for a in xpath(data, '//h:a[@href]|//h:i|//h:b|//h:u'):
                 if a.get('id', None) is None and a.get('name', None) is None \
                         and len(a) == 0 and not a.text:
                     remove_elem(a)