diff --git a/src/private/ConvertFrom-SizeString.ps1 b/src/private/ConvertFrom-SizeString.ps1
index 92f474f..6dc8363 100644
--- a/src/private/ConvertFrom-SizeString.ps1
+++ b/src/private/ConvertFrom-SizeString.ps1
@@ -1,6 +1,6 @@
 function ConvertFrom-SizeString {
     param(
-        [parameter(Mandatory, ValueFromPipeline)]
+        [parameter(Mandatory = $true, ValueFromPipeline = $true)]
         [string]
         $String
     )
diff --git a/src/private/Get-DiskPartDisk.ps1 b/src/private/Get-DiskPartDisk.ps1
index 5319f3d..3ca302c 100644
--- a/src/private/Get-DiskPartDisk.ps1
+++ b/src/private/Get-DiskPartDisk.ps1
@@ -77,9 +77,9 @@ function Get-DiskPartDisk {
 
                         # if DiskID is a guid then partitionstyle is GPT
                         # otherwises its RAW, MBR or something else
-                        if ([guid]::TryParse($DiskID, ([ref]$DiskID))) {
-                            $Disk.PartitionStyle = "GPT"
-                        } else {
+                        try {
+                            [guid]::Parse($DiskID) | Out-Null ; $Disk.PartitionStyle = "GPT"
+                        } catch {
                             if ($DiskID -eq "00000000") {
                                 $Disk.PartitionStyle = "RAW"
                             } elseif ($DiskID -match "^[\d\w]{8}$") {