Backtick and @ at start of inner line wrongly marked as error inside plain literal block scalar

[estan]

For example:

foo: |
  This is
  `a literal

bar: |
  And
  @this

The ` and @ are marked as errors

when they are in fact allowed. They are only disallowed if they start the plain scalar (see Example 5.10 in the 1.1 spec), but not when used inside the scalar like this.

This is with PyCharm Community Edition 2016.3 and SnakeYAML plugin 1.17.0.

SnakeYAML itself behaves correctly on this, so the problem must be within the plugin.