Using Powershell to Update "manager" attribute in AD

Hello,

I have a csv file that I use this to update all the AD attributes.

The CSV file looks like this:
EmployeeID,Title,managerID,Department,physicalDeliveryOfficeName,StreetAddress,L,ST,postalCode
11111,Engineer,22222,My Department,"111 main st., Suite 105",somecity,MD,22244

Below is the script I use to update the AD attributes:
Import-Module ActiveDirectory
Import-Csv update.csv | ForEach `
{
$mgr=Get-ADUser -LDAPFilter "(employeeID=$_.managerID)" | Select -ExpandProperty DistinguishedName
Get-ADUser -LDAPFilter "(employeeID=$_.employeeID)" -properties * |Set-ADUser -replace @{title=$title;manager=$mgr}
}

If I remove manager=$mgr the script works with no problems.

If I put it back it fails with error message:
----------------------------------------------------------------------------------------------------------------------------
Set-ADUser : Cannot bind parameter 'Replace' to the target. Exception setting "
Replace": "Object reference not set to an instance of an object."
At C:\temp\ad\userInfo.ps1:16 char:91
+     Get-ADUser -LDAPFilter "(employeeID=$_.employeeID)" -properties * |Set-AD
User -replace <<<<  @{title=$title;manager=$mgr}
    + CategoryInfo          : WriteError: (:) [Set-ADUser], ParameterBindingEx
   ception
    + FullyQualifiedErrorId : ParameterBindingFailed,Microsoft.ActiveDirectory
   .Management.Commands.SetADUser
-------------------------------------------------------------------------------------------------------------------------------

I tried putting quotes around $mgr but it still did not work.  
The weird part is if I type one by one on the powershell window it works fine.

Any ideas what the issue could be?

Thanks!