diff --git a/nbconvert/preprocessors/csshtmlheader.py b/nbconvert/preprocessors/csshtmlheader.py
index 4feff8fed..191a2ea6c 100755
--- a/nbconvert/preprocessors/csshtmlheader.py
+++ b/nbconvert/preprocessors/csshtmlheader.py
@@ -78,47 +78,6 @@ def _generate_header(self, resources):
         pygments_css = formatter.get_style_defs(self.highlight_class)
         header.append(pygments_css)
 
-        # These ANSI CSS definitions will be part of style.min.css with the
-        # Notebook release 5.0 and shall be removed afterwards!
-        # See https://github.com/jupyter/nbconvert/pull/259
-        header.append("""
-/* Temporary definitions which will become obsolete with Notebook release 5.0 */
-.ansi-black-fg { color: #3E424D; }
-.ansi-black-bg { background-color: #3E424D; }
-.ansi-black-intense-fg { color: #282C36; }
-.ansi-black-intense-bg { background-color: #282C36; }
-.ansi-red-fg { color: #E75C58; }
-.ansi-red-bg { background-color: #E75C58; }
-.ansi-red-intense-fg { color: #B22B31; }
-.ansi-red-intense-bg { background-color: #B22B31; }
-.ansi-green-fg { color: #00A250; }
-.ansi-green-bg { background-color: #00A250; }
-.ansi-green-intense-fg { color: #007427; }
-.ansi-green-intense-bg { background-color: #007427; }
-.ansi-yellow-fg { color: #DDB62B; }
-.ansi-yellow-bg { background-color: #DDB62B; }
-.ansi-yellow-intense-fg { color: #B27D12; }
-.ansi-yellow-intense-bg { background-color: #B27D12; }
-.ansi-blue-fg { color: #208FFB; }
-.ansi-blue-bg { background-color: #208FFB; }
-.ansi-blue-intense-fg { color: #0065CA; }
-.ansi-blue-intense-bg { background-color: #0065CA; }
-.ansi-magenta-fg { color: #D160C4; }
-.ansi-magenta-bg { background-color: #D160C4; }
-.ansi-magenta-intense-fg { color: #A03196; }
-.ansi-magenta-intense-bg { background-color: #A03196; }
-.ansi-cyan-fg { color: #60C6C8; }
-.ansi-cyan-bg { background-color: #60C6C8; }
-.ansi-cyan-intense-fg { color: #258F8F; }
-.ansi-cyan-intense-bg { background-color: #258F8F; }
-.ansi-white-fg { color: #C5C1B4; }
-.ansi-white-bg { background-color: #C5C1B4; }
-.ansi-white-intense-fg { color: #A1A6B2; }
-.ansi-white-intense-bg { background-color: #A1A6B2; }
-
-.ansi-bold { font-weight: bold; }
-""")
-
         # Load the user's custom CSS and IPython's default custom CSS.  If they
         # differ, assume the user has made modifications to his/her custom CSS
         # and that we should inline it in the nbconvert output.