Domain creation: Invalid name format

We are attempting to create a tree domain in our network. When creating the domain we are getting the error listed below. We've double checked the naming to make sure it does not include any special characters. If we change the ".edu" to anything else, such as ".local" it progresses without the error, but we really need to use the original domain name. I've also listed the powershell script used to run the domain promotion below the error message:

Install-ADDSDomain : Verification of prerequisites for Domain Controller promotion failed. The domain >DNS name "pennco.edu" has an invalid format. DNS names can contain letters, numbers, and hyphens, but not spaces. Periods are used to separate domain >labels, which can be no longer than 63 bytes. The top-level domain name must contain at least one non-numeric character. Characters that are not allowed include: ! " # $ & ( ) * + , ' / : ; < = > ? @ [ \ ] ^ { | } ~ Example: domain-1.microsoft.com. At line:2 char:1 + Install-ADDSDomain + ~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : NotSpecified: (:) [Install-ADDSDomain], TestFailedException + FullyQualifiedErrorId : >Test.VerifyDcPromoCore.DCPromo.General.48,Microsoft.DirectoryServices.Deployment.PowerShell.Commands.Ins>tallADDSDomainCommand

Import-Module ADDSDeployment
Install-ADDSDomain `
-NoGlobalCatalog:$false `
-CreateDnsDelegation:$false `
-Credential (Get-Credential) `
-DatabasePath "C:\Windows\NTDS" `
-DomainMode "Win2012R2" `
-DomainType "TreeDomain" `
-InstallDns:$true `
-LogPath "C:\Windows\NTDS" `
-NewDomainName "pennco.edu" `
-NewDomainNetbiosName "PENNCO" `
-ParentDomainName "PenncoDomain.edu" `
-NoRebootOnCompletion:$false `
-SiteName "Penncodomian" `
-SysvolPath "C:\Windows\SYSVOL" `
-Force:$true