Change checkbox value

observations/templates/observations/index.html

@@ -56,7 +56,7 @@
             </div>
             <div class="checkbox">
                 <label>
-                  <input type="checkbox" name="includeNegative"{% if include_negative  %}checked{% endif %}> {% trans "Include registrations without pest presence" %}
+                  <input type="checkbox" name="includeNegative"{% if include_negative  %}checked{% endif %} value="true"> {% trans "Include registrations without pest presence" %}
                 </label>
               </div>
             <button type="submit" class="btn btn-primary">{% trans "Filter" %}</button>