--- a/tests/run-tests.py	Tue Oct 17 11:07:18 2017 -0700
+++ b/tests/run-tests.py	Tue Oct 17 10:33:27 2017 -0700
@@ -1663,7 +1663,9 @@
                     self.stream.write('t')
                 else:
                     if not self._options.nodiff:
-                        formatted = '\nERROR: %s output changed\n' % test
+                        self.stream.write('\n')
+                        # Exclude the '\n' from highlighting to lex correctly
+                        formatted = 'ERROR: %s output changed\n' % test
                         self.stream.write(highlightmsg(formatted, self.color))
                     self.stream.write('!')