TemplateSyntaxError: expected token 'end of statement block', got '%'

I'm going through the flask megatutorial by Miguel G. right now and I've hit this problem where when try to boot up the application using template inheritance for the html structure, I come across this error:

TemplateSyntaxError: expected token 'end of statement block', got '%'.

My code looks like this, for reference.

<html>
{% extends "base.html" %}
{% block content % }
        <h1> Hello, {{user.nickname}}! </h1>
        {% for post in posts %}
        <div><p>{{post.author.nickname}} says: <b>{{post.body}}</b>/<p></div>
        {% endfor %}
{% endblock %}
</html>
~        

any advice on what's going wrong with this would be greatly appreciated. Thanks!