matching fails unless content begins with space

[jason-ha]

Using rule:
'header/header': [2, 'line', 'my header comment.']
with file:

// my header comment.
console.log(1);

reports incorrect header. Changing rule to:
'header/header': [2, 'line', ' my header comment.']
will not report error and unblocks use.

In both rule cases --fix will produce:

// my header comment.
console.log(1);

if error is detected. (Added line per issue #24 Autofix adds new line has been removed.)

In my setup, I am using eslint 6.8.0.