diff --git a/src/calibre/ebooks/html/input.py b/src/calibre/ebooks/html/input.py
index ce6c46c6cf..69eb493c7d 100644
--- a/src/calibre/ebooks/html/input.py
+++ b/src/calibre/ebooks/html/input.py
@@ -457,7 +457,7 @@ class HTMLInput(InputFormatPlugin):
                     href=bhref)
             guessed = self.guess_type(href)[0]
             media_type = guessed or self.BINARY_MIME
-            if 'text' in media_type:
+            if media_type == 'text/plain':
                 self.log.warn('Ignoring link to text file %r'%link_)
                 return None
 
diff --git a/src/calibre/ebooks/oeb/base.py b/src/calibre/ebooks/oeb/base.py
index a9c7664953..d75620adbd 100644
--- a/src/calibre/ebooks/oeb/base.py
+++ b/src/calibre/ebooks/oeb/base.py
@@ -1162,7 +1162,7 @@ class Manifest(object):
                     data = self._parse_xml(data)
                 elif self.media_type.lower() in OEB_STYLES:
                     data = self._parse_css(data)
-                elif 'text' in self.media_type.lower():
+                elif self.media_type.lower() == 'text/plain':
                     self.oeb.log.warn('%s contains data in TXT format'%self.href,
                             'converting to HTML')
                     data = self._parse_txt(data)