Date_column=”post_modified_date” not working?

I tried to display all posts which are modified in the last two months.

I wrote this shortcode:
[display-posts date_query_after=”-2 months” date_query_column=”post_modified_date” orderby=”modified”]

but the result was that the selection is done on post_date and not post_modified_date

I have tried to use data_column=”post_modified_date” but the result is the same.

Am I doing it wrong? I appreciate your help.

I use the Twenty-Fifteen theme.