TYPO3 Core

I have installed and uninstalled extension (pt_extbase), than removed it from server. If i want now upload this extension on the server again it is impossible as EM returns error message "Extension is already available and overwriting was not enabled." (see the attached image).

I'm not sure how this all works now internally, but inside typo3conf/PackageStates.php i have existing entry:

'pt_extbase' =>
array (
'state' => 'inactive',
'packagePath' => 'typo3conf/ext/pt_extbase/',
'classesPath' => 'Classes/',
),

So, it looks like EM checks if package is listed but not if it exists on server?

If i check "Overwite" checkbox in upload form, the extension is uploaded without any problems and installed.