AD Powershell - Adding ProxyAddresses to Groups from CSV

I have a set of AD Groups that I want to populate the ProxyAddresses of using a CSV File.

My CSV looks like this:

identity,proxyaddresses

group1,grp1@test.com;grp1@test.org;grp1@test.net

group2,grp2@test.com;grp2@test.org;grp2@test.net

Import-CSV "C:\import_proxy.csv"| % {Set-ADGroup -identity $_.identity -Add @{proxyAddresses = ($_.proxy -split ";")}}

I'm getting an error:

+ Import-CSV "C:\import_proxy.csv"| % {Set-ADGroup <<<<  -identity $_.identity -Add @{proxyAddresses = ($_.proxy -split ";")}}
    + CategoryInfo          : InvalidOperation: (testgroup8:ADGroup) [Set-ADGroup], ADInvalidOperationException
    + FullyQualifiedErrorId : add,Microsoft.ActiveDirectory.Management.Commands.SetADGroup

What am I doing wrong and how can I get this to work?

Thanks!