diff --git a/src/calibre/ebooks/mobi/reader.py b/src/calibre/ebooks/mobi/reader.py
index 04637ffa89..e4b40616ba 100644
--- a/src/calibre/ebooks/mobi/reader.py
+++ b/src/calibre/ebooks/mobi/reader.py
@@ -325,6 +325,10 @@ class MobiReader(object):
         self.processed_html = self.processed_html.replace('</</', '</')
         self.processed_html = re.sub(r'</([a-zA-Z]+)<', r'</\1><',
                 self.processed_html)
+        # Remove tags of the form <xyz: ...> as they can cause issues further
+        # along the pipeline
+        self.processed_html = re.sub(r'</{0,1}[a-zA-Z]+:\s+[^>]*>', '',
+                self.processed_html)
 
         for pat in ENCODING_PATS:
             self.processed_html = pat.sub('', self.processed_html)