diff --git a/windows/image/installers/install-tbb.ps1 b/windows/image/installers/install-tbb.ps1
index 2794ed10..3dc631fa 100644
--- a/windows/image/installers/install-tbb.ps1
+++ b/windows/image/installers/install-tbb.ps1
@@ -4,8 +4,9 @@ Expand-Archive .\tbb.zip
 Remove-Item .\tbb.zip
 
 $cwd = Get-Location
+$LOCAL_TBB_ROOT = "$cwd\tbb\oneapi-tbb-$TBB_VERSION"
 
 . "$PSScriptRoot/envvars.ps1"
 
-Set-MachineEnvironmentVariable -Append -Variable "PATH" -Value "$ENV:TBB_ROOT\redist\intel64\vc14\"
-Set-MachineEnvironmentVariable -Variable "TBB_ROOT" -Value "$cwd\tbb\oneapi-tbb-$TBB_VERSION"
+Set-MachineEnvironmentVariable -Append -Variable "PATH" -Value "$LOCAL_TBB_ROOT\redist\intel64\vc14\"
+Set-MachineEnvironmentVariable -Variable "TBB_ROOT" -Value "$LOCAL_TBB_ROOT"