Validation rule on Picklist value on Global Action

I have created a Global Action ‘Log a Call Custom’

Here on the Task object I have a Picklist field Subject with four values –

‘Please Select
‘Option 1’
‘Option 2’
‘Option 3’

The default is ‘Please Select’

I created a validation rule to prevent a user from saving the activity if the value in subject is ‘Please Select’

This is my validation rule

ISPICKVAL (Subject, Please Select)

However i am getting a syntax error

Error: Syntax error. Missing ‘)’

what am i mising?