Django template variable value to string literal comparison fails

I have the following code in my template that supposed to compare the value of watchinstance.shift, which can be either "DAY" or "NIGHT", to a literal string "DAY". The comparisson always fails.

{% for watchinstance in watchinstance_list %}
    {% if watchinstance.shift == "DAY" %}
        <p>shift is DAY</p>
    {% endif %}
{% endfor %}

Using ifequal doesn't work either:

{% for watchinstance in watchinstance_list %}
    {% ifequal watchinstance.shift "DAY" %}
        <p>shift is DAY</p>
    {% endifequal %}
{% endfor %}

However, just calling {{ watchinstance.shift }} works as expected:

{% for watchinstance in watchinstance_list %}
    {{ watchinstance.shift }}
{% endfor %}

returns DAYs and NIGHTs.

I checked whether watchinstance.shift returns any extra characters, and it doesn't look like it does... What else can I be missing here?