Error with default value of a date parameter

I have a parameter with a data type of date/time.

I am trying to set the default value based on a dataset.

The dataset only has one row and one column.

I have verified by the IsDate function that the dataset column is a date column.

I have set the default value of the date parameter to the only column of this dataset.

However, when I run the report I get an error:

The property 'DefaultValue' of report paracter EndDate doesn't have the expected type.

Any ideas?

Thank you.