Weird Question About OVER PARTITION BY Query

I guess today is just my day to be confused...I feel really stupid as i've used the OVER (PARTITION) clause quite a bit.

I'm wondering why my query isn't returning row numbers properly, i'm getting 1's when I should be getting 1,2, 3, etc.  I don't understand.  I have a very simple DDL which I created for test, take a look -

DROP TABLE #Table

CREATE TABLE #Table
(
	IssueID			INT 
	,DateUpdated	DATE
)

INSERT INTO #Table VALUES (1324, '2014-02-02')
INSERT INTO #Table VALUES (1463, '2014-02-07')

SELECT 
	ROW_NUMBER() OVER (PARTITION BY IssueID ORDER BY DateUpdated) as RowNumber
	,IssueID
	,DateUpdated
FROM #Table